diff --git a/papers/newIns.md b/papers/newIns.md
index d983a3d2e..32152bd32 100644
--- a/papers/newIns.md
+++ b/papers/newIns.md
@@ -192,6 +192,7 @@ size | description
   1  | |x| ALG |x| FB  |
   1  | |FMS2 |AMS| FMS |
   1  | |AM2|4| LLPatch |
+  1  | |xxxxxxx| Block | (>=224)
 -----|------------------------------------
      | **operator data × opCount**
      | /7 6 5 4 3 2 1 0|
diff --git a/src/engine/bsr.h b/src/engine/bsr.h
index dcc865112..566125383 100644
--- a/src/engine/bsr.h
+++ b/src/engine/bsr.h
@@ -44,7 +44,7 @@ static inline int bsr32(unsigned int v) {
 
 static inline int bsr(unsigned short v) {
   if (v) {
-    return 32 - __builtin_clz(v);
+    return 32-__builtin_clz(v);
   } else {
     return -1;
   }
@@ -52,7 +52,7 @@ static inline int bsr(unsigned short v) {
 
 static inline int bsr32(unsigned int v) {
   if (v) {
-    return 32 - __builtin_clz(v);
+    return 32-__builtin_clz(v);
   } else {
     return -1;
   }
@@ -61,25 +61,52 @@ static inline int bsr32(unsigned int v) {
 #else
 
 static inline int bsr(unsigned short v) {
-  unsigned short mask = 0x8000;
-  for (int i = 16; i >= 0; --i) {
-    if (v&mask)
-      return i;
-    mask>>=1;
+  if (v==0) return -1;
+  if (v&0x8000) return 16;
+  int o=16;
+  if (!(v&0xff00)) {
+    o-=8;
+    v<<=8;
+    if (v&0x8000) return o;
   }
-
-  return -1;
+  if (!(v&0xf000)) {
+    o-=4;
+    v<<=4;
+    if (v&0x8000) return o;
+  }
+  if (!(v&0xc000)) {
+    o-=2;
+    v<<=2;
+    if (v&0x8000) return o;
+  }
+  return (v&0x8000) ? o : o-1;
 }
 
 static inline int bsr32(unsigned int v) {
-  unsigned int mask = 0x80000000;
-  for (int i = 32; i >= 0; --i) {
-    if (v&mask)
-      return i;
-    mask>>=1;
+  if (v==0) return -1;
+  if (v&0x80000000) return 32;
+  int o=32;
+  if (!(v&0xffff0000)) {
+    o-=16;
+    v<<=16;
+    if (v&0x80000000) return o;
   }
-
-  return -1;
+  if (!(v&0xff000000)) {
+    o-=8;
+    v<<=8;
+    if (v&0x80000000) return o;
+  }
+  if (!(v&0xf0000000)) {
+    o-=4;
+    v<<=4;
+    if (v&0x80000000) return o;
+  }
+  if (!(v&0xc0000000)) {
+    o-=2;
+    v<<=2;
+    if (v&0x80000000) return o;
+  }
+  return (v&0x80000000) ? o : o-1;
 }
 
 #endif
diff --git a/src/engine/dispatch.h b/src/engine/dispatch.h
index c74129959..fe1ac421a 100644
--- a/src/engine/dispatch.h
+++ b/src/engine/dispatch.h
@@ -948,7 +948,7 @@ class DivDispatch {
 #define NOTE_FREQUENCY(x) parent->calcBaseFreq(chipClock,CHIP_FREQBASE,x,false)
 
 // this is a special case definition. only use it for f-num/block-based chips.
-#define NOTE_FNUM_BLOCK(x,bits) parent->calcBaseFreqFNumBlock(chipClock,CHIP_FREQBASE,x,bits)
+#define NOTE_FNUM_BLOCK(x,bits,blk) parent->calcBaseFreqFNumBlock(chipClock,CHIP_FREQBASE,x,bits,blk)
 
 // this is for volume scaling calculation.
 #define VOL_SCALE_LINEAR(x,y,range) ((parent->song.ceilVolumeScaling)?((((x)*(y))+(range-1))/(range)):(((x)*(y))/(range)))
diff --git a/src/engine/engine.cpp b/src/engine/engine.cpp
index f50bbc753..850dd98b4 100644
--- a/src/engine/engine.cpp
+++ b/src/engine/engine.cpp
@@ -1797,15 +1797,27 @@ double DivEngine::calcBaseFreq(double clock, double divider, int note, bool peri
   /* logV("f-num: %d block: %d",bf,block); */ \
   return bf|(block<<bits);
 
-int DivEngine::calcBaseFreqFNumBlock(double clock, double divider, int note, int bits) {
+#define CONVERT_FNUM_FIXEDBLOCK(bf,bits,block) \
+  bf>>=(block); \
+  if (bf<0) bf=0; \
+  if (bf>((1<<(bits))-1)) { \
+    bf=(1<<(bits))-1; \
+  } \
+  return bf|((block)<<(bits));
+
+int DivEngine::calcBaseFreqFNumBlock(double clock, double divider, int note, int bits, int fixedBlock) {
   if (song.linearPitch==2) { // full linear
     return (note<<7);
   }
   int bf=calcBaseFreq(clock,divider,note,false);
-  CONVERT_FNUM_BLOCK(bf,bits,note)
+  if (fixedBlock>0) {
+    CONVERT_FNUM_FIXEDBLOCK(bf,bits,fixedBlock-1);
+  } else {
+    CONVERT_FNUM_BLOCK(bf,bits,note);
+  }
 }
 
-int DivEngine::calcFreq(int base, int pitch, int arp, bool arpFixed, bool period, int octave, int pitch2, double clock, double divider, int blockBits) {
+int DivEngine::calcFreq(int base, int pitch, int arp, bool arpFixed, bool period, int octave, int pitch2, double clock, double divider, int blockBits, int fixedBlock) {
   if (song.linearPitch==2) {
     // do frequency calculation here
     int nbase=base+pitch+pitch2;
@@ -1821,7 +1833,11 @@ int DivEngine::calcFreq(int base, int pitch, int arp, bool arpFixed, bool period
            round((clock/fbase)/divider):
            round(fbase*(divider/clock));
     if (blockBits>0) {
-      CONVERT_FNUM_BLOCK(bf,blockBits,nbase>>7)
+      if (fixedBlock>0) {
+        CONVERT_FNUM_FIXEDBLOCK(bf,blockBits,fixedBlock-1);
+      } else {
+        CONVERT_FNUM_BLOCK(bf,blockBits,nbase>>7);
+      }
     } else {
       return bf;
     }
diff --git a/src/engine/engine.h b/src/engine/engine.h
index c64268dd8..5b6a83c51 100644
--- a/src/engine/engine.h
+++ b/src/engine/engine.h
@@ -54,8 +54,8 @@ class DivWorkPool;
 
 #define DIV_UNSTABLE
 
-#define DIV_VERSION "dev223"
-#define DIV_ENGINE_VERSION 223
+#define DIV_VERSION "dev224"
+#define DIV_ENGINE_VERSION 224
 // for imports
 #define DIV_VERSION_MOD 0xff01
 #define DIV_VERSION_FC 0xff02
@@ -805,10 +805,10 @@ class DivEngine {
     double calcBaseFreq(double clock, double divider, int note, bool period);
 
     // calculate base frequency in f-num/block format
-    int calcBaseFreqFNumBlock(double clock, double divider, int note, int bits);
+    int calcBaseFreqFNumBlock(double clock, double divider, int note, int bits, int fixedBlock);
 
     // calculate frequency/period
-    int calcFreq(int base, int pitch, int arp, bool arpFixed, bool period=false, int octave=0, int pitch2=0, double clock=1.0, double divider=1.0, int blockBits=0);
+    int calcFreq(int base, int pitch, int arp, bool arpFixed, bool period=false, int octave=0, int pitch2=0, double clock=1.0, double divider=1.0, int blockBits=0, int fixedBlock=0);
 
     // calculate arpeggio
     int calcArp(int note, int arp, int offset=0);
diff --git a/src/engine/instrument.cpp b/src/engine/instrument.cpp
index 18ef4a31c..f068015cd 100644
--- a/src/engine/instrument.cpp
+++ b/src/engine/instrument.cpp
@@ -409,6 +409,7 @@ void DivInstrument::writeFeatureFM(SafeWriter* w, bool fui) {
   w->writeC(((fm.alg&7)<<4)|(fm.fb&7));
   w->writeC(((fm.fms2&7)<<5)|((fm.ams&3)<<3)|(fm.fms&7));
   w->writeC(((fm.ams2&3)<<6)|((fm.ops==4)?32:0)|(fm.opllPreset&31));
+  w->writeC(fm.block&15);
 
   // operator data
   for (int i=0; i<opCount; i++) {
@@ -1741,6 +1742,11 @@ void DivInstrument::readFeatureFM(SafeReader& reader, short version) {
   fm.ops=(next&32)?4:2;
   fm.opllPreset=next&31;
 
+  if (version>=224) {
+    next=reader.readC();
+    fm.block=next&15;
+  }
+
   // read operators
   for (int i=0; i<opCount; i++) {
     DivInstrumentFM::Operator& op=fm.op[i];
diff --git a/src/engine/instrument.h b/src/engine/instrument.h
index a1aec2cae..78d6f185a 100644
--- a/src/engine/instrument.h
+++ b/src/engine/instrument.h
@@ -165,7 +165,7 @@ enum DivMacroTypeOp: unsigned char {
 //   - WS, DVB = MULT (FINE), DAM = REV, KSL = EGShift, EGT = Fixed
 
 struct DivInstrumentFM {
-  unsigned char alg, fb, fms, ams, fms2, ams2, ops, opllPreset;
+  unsigned char alg, fb, fms, ams, fms2, ams2, ops, opllPreset, block;
   bool fixedDrums;
   unsigned short kickFreq, snareHatFreq, tomTopFreq;
 
@@ -216,6 +216,7 @@ struct DivInstrumentFM {
     ams2(0),
     ops(2),
     opllPreset(0),
+    block(0),
     fixedDrums(false),
     kickFreq(0x520),
     snareHatFreq(0x550),
diff --git a/src/engine/platform/esfm.cpp b/src/engine/platform/esfm.cpp
index 3adab20f5..8b3d48b75 100644
--- a/src/engine/platform/esfm.cpp
+++ b/src/engine/platform/esfm.cpp
@@ -19,6 +19,7 @@
 
 #include "esfm.h"
 #include "../engine.h"
+#include "../bsr.h"
 #include "../../ta-log.h"
 #include <string.h>
 #include <stdio.h>
@@ -291,7 +292,12 @@ void DivPlatformESFM::tick(bool sysTick) {
 
   for (int i=0; i<18; i++) {
     if (chan[i].freqChanged) {
-      chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,octave(chan[i].baseFreq)*2,chan[i].pitch2,chipClock,CHIP_FREQBASE);
+      int mul=2;
+      int fixedBlock=chan[i].state.fm.block;
+      if (parent->song.linearPitch!=2) {
+        mul=octave(chan[i].baseFreq,fixedBlock)*2;
+      }
+      chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,mul,chan[i].pitch2,chipClock,CHIP_FREQBASE);
       if (chan[i].freq<0) chan[i].freq=0;
       if (chan[i].freq>131071) chan[i].freq=131071;
 
@@ -314,10 +320,10 @@ void DivPlatformESFM::tick(bool sysTick) {
           if(chan[i].opsState[o].hasOpPitch) {
             pitch2=chan[i].opsState[o].pitch2+dt;
           }
-          int opFreq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,arp,fixedArp,false,octave(chan[i].baseFreq)*2,pitch2,chipClock,CHIP_FREQBASE);
+          int opFreq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,arp,fixedArp,false,mul,pitch2,chipClock,CHIP_FREQBASE);
           if (opFreq<0) opFreq=0;
           if (opFreq>131071) opFreq=131071;
-          int freqt=toFreq(opFreq);
+          int freqt=toFreq(opFreq,fixedBlock);
           chan[i].freqL[o]=freqt&0xff;
           chan[i].freqH[o]=freqt>>8;
         }
@@ -365,22 +371,27 @@ void DivPlatformESFM::tick(bool sysTick) {
   }
 }
 
-int DivPlatformESFM::octave(int freq) {
-  int result=1;
-  while (freq>0x3ff) {
-    freq>>=1;
-    result<<=1;
+int DivPlatformESFM::octave(int freq, int fixedBlock) {
+  if (fixedBlock>0) {
+    return 1<<(fixedBlock-1);
   }
-  return result;
+  if (freq>0x3ff) {
+    return 1<<(bsr32(freq)-10);
+  }
+  return 1;
 }
 
-int DivPlatformESFM::toFreq(int freq) {
+int DivPlatformESFM::toFreq(int freq, int fixedBlock) {
   int block=0;
-  while (freq>0x3ff) {
-    freq>>=1;
-    block++;
+  if (fixedBlock>0) {
+    block=fixedBlock-1;
+    freq>>=block;
+    if (freq>0x3ff) freq=0x3ff;
+  } else if (freq>0x3ff) {
+    block=bsr32(freq)-10;
+    freq>>=block;
   }
-  return ((block&7)<<10)|(freq&0x3ff);
+  return (block<<10)|(freq&0x3ff);
 }
 
 void DivPlatformESFM::muteChannel(int ch, bool mute) {
@@ -513,21 +524,27 @@ int DivPlatformESFM::dispatch(DivCommand c) {
       int destFreq=NOTE_FREQUENCY(c.value2);
       int newFreq;
       bool return2=false;
+      int mul=1;
+      int fixedBlock=0;
+      if (parent->song.linearPitch!=2) {
+        fixedBlock=chan[c.chan].state.fm.block;
+        mul=octave(chan[c.chan].baseFreq,fixedBlock);
+      }
       if (destFreq>chan[c.chan].baseFreq) {
-        newFreq=chan[c.chan].baseFreq+c.value*((parent->song.linearPitch==2)?1:octave(chan[c.chan].baseFreq));
+        newFreq=chan[c.chan].baseFreq+c.value*mul;
         if (newFreq>=destFreq) {
           newFreq=destFreq;
           return2=true;
         }
       } else {
-        newFreq=chan[c.chan].baseFreq-c.value*((parent->song.linearPitch==2)?1:octave(chan[c.chan].baseFreq));
+        newFreq=chan[c.chan].baseFreq-c.value*mul;
         if (newFreq<=destFreq) {
           newFreq=destFreq;
           return2=true;
         }
       }
       if (!chan[c.chan].portaPause && parent->song.linearPitch!=2) {
-        if (octave(chan[c.chan].baseFreq)!=octave(newFreq)) {
+        if (mul!=octave(newFreq,fixedBlock)) {
           chan[c.chan].portaPause=true;
           break;
         }
diff --git a/src/engine/platform/esfm.h b/src/engine/platform/esfm.h
index 8321369bf..a46e12079 100644
--- a/src/engine/platform/esfm.h
+++ b/src/engine/platform/esfm.h
@@ -126,8 +126,8 @@ class DivPlatformESFM: public DivDispatch {
   short oldWrites[ESFM_REG_POOL_SIZE];
   short pendingWrites[ESFM_REG_POOL_SIZE];
 
-  int octave(int freq);
-  int toFreq(int freq);
+  int octave(int freq, int fixedBlock);
+  int toFreq(int freq, int fixedBlock);
   void commitState(int ch, DivInstrument* ins);
 
   friend void putDispatchChip(void*,int);
diff --git a/src/engine/platform/fmshared_OPN.h b/src/engine/platform/fmshared_OPN.h
index 6c29ecf93..7f4a21c01 100644
--- a/src/engine/platform/fmshared_OPN.h
+++ b/src/engine/platform/fmshared_OPN.h
@@ -24,10 +24,10 @@
 #include "../../../extern/opn/ym3438.h"
 #include "sound/ymfm/ymfm_opn.h"
 
-#define PLEASE_HELP_ME(_targetChan) \
+#define PLEASE_HELP_ME(_targetChan,blk) \
   int boundaryBottom=parent->calcBaseFreq(chipClock,CHIP_FREQBASE,0,false); \
   int boundaryTop=parent->calcBaseFreq(chipClock,CHIP_FREQBASE,12,false); \
-  int destFreq=NOTE_FNUM_BLOCK(c.value2,11); \
+  int destFreq=NOTE_FNUM_BLOCK(c.value2,11,blk); \
   int newFreq; \
   bool return2=false; \
   if (_targetChan.portaPause) { \
diff --git a/src/engine/platform/genesis.cpp b/src/engine/platform/genesis.cpp
index a2cfc7fbb..836cbea0c 100644
--- a/src/engine/platform/genesis.cpp
+++ b/src/engine/platform/genesis.cpp
@@ -657,7 +657,7 @@ void DivPlatformGenesis::tick(bool sysTick) {
         chan[i].handleArp();
       } else if (chan[i].std.arp.had) {
         if (!chan[i].inPorta) {
-          chan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(chan[i].note,chan[i].std.arp.val),11);
+          chan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(chan[i].note,chan[i].std.arp.val),11,chan[i].state.block);
         }
         chan[i].freqChanged=true;
       }
@@ -838,7 +838,7 @@ void DivPlatformGenesis::tick(bool sysTick) {
     if (i==2 && extMode) continue;
     if (chan[i].freqChanged) {
       if (parent->song.linearPitch==2) {
-        chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,2,chan[i].pitch2,chipClock,CHIP_FREQBASE,11);
+        chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,2,chan[i].pitch2,chipClock,CHIP_FREQBASE,11,chan[i].state.block);
       } else {
         int fNum=parent->calcFreq(chan[i].baseFreq&0x7ff,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,2,chan[i].pitch2,chipClock,CHIP_FREQBASE,11);
         int block=(chan[i].baseFreq&0xf800)>>11;
@@ -1084,7 +1084,7 @@ int DivPlatformGenesis::dispatch(DivCommand c) {
       chan[c.chan].insChanged=false;
 
       if (c.value!=DIV_NOTE_NULL) {
-        chan[c.chan].baseFreq=NOTE_FNUM_BLOCK(c.value,11);
+        chan[c.chan].baseFreq=NOTE_FNUM_BLOCK(c.value,11,chan[c.chan].state.block);
         chan[c.chan].portaPause=false;
         chan[c.chan].note=c.value;
         chan[c.chan].freqChanged=true;
@@ -1235,7 +1235,7 @@ int DivPlatformGenesis::dispatch(DivCommand c) {
         }
         break;
       }
-      PLEASE_HELP_ME(chan[c.chan]);
+      PLEASE_HELP_ME(chan[c.chan],chan[c.chan].state.block);
       break;
     }
     case DIV_CMD_SAMPLE_MODE: {
@@ -1274,7 +1274,7 @@ int DivPlatformGenesis::dispatch(DivCommand c) {
           commitState(c.chan,ins);
           chan[c.chan].insChanged=false;
         }
-        chan[c.chan].baseFreq=NOTE_FNUM_BLOCK(c.value,11);
+        chan[c.chan].baseFreq=NOTE_FNUM_BLOCK(c.value,11,chan[c.chan].state.block);
       }
       chan[c.chan].note=c.value;
       chan[c.chan].freqChanged=true;
diff --git a/src/engine/platform/genesisext.cpp b/src/engine/platform/genesisext.cpp
index 3ff9fc53c..b8b5ac666 100644
--- a/src/engine/platform/genesisext.cpp
+++ b/src/engine/platform/genesisext.cpp
@@ -96,7 +96,7 @@ int DivPlatformGenesisExt::dispatch(DivCommand c) {
       opChan[ch].insChanged=false;
 
       if (c.value!=DIV_NOTE_NULL) {
-        opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11);
+        opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11,chan[extChanOffs].state.alg);
         opChan[ch].portaPause=false;
         opChan[ch].note=c.value;
         opChan[ch].freqChanged=true;
@@ -191,7 +191,7 @@ int DivPlatformGenesisExt::dispatch(DivCommand c) {
         }
         break;
       }
-      PLEASE_HELP_ME(opChan[ch]);
+      PLEASE_HELP_ME(opChan[ch],chan[extChanOffs].state.block);
       break;
     }
     case DIV_CMD_SAMPLE_MODE: {
@@ -216,7 +216,7 @@ int DivPlatformGenesisExt::dispatch(DivCommand c) {
         commitStateExt(ch,ins);
         opChan[ch].insChanged=false;
       }
-      opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11);
+      opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11,chan[extChanOffs].state.alg);
       opChan[ch].freqChanged=true;
       break;
     }
@@ -517,7 +517,7 @@ void DivPlatformGenesisExt::tick(bool sysTick) {
 
     if (opChan[i].std.arp.had) {
       if (!opChan[i].inPorta) {
-        opChan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(opChan[i].note,opChan[i].std.arp.val),11);
+        opChan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(opChan[i].note,opChan[i].std.arp.val),11,chan[extChanOffs].state.alg);
       }
       opChan[i].freqChanged=true;
     }
@@ -638,7 +638,7 @@ void DivPlatformGenesisExt::tick(bool sysTick) {
   if (extMode) for (int i=0; i<4; i++) {
     if (opChan[i].freqChanged) {
       if (parent->song.linearPitch==2) {
-        opChan[i].freq=parent->calcFreq(opChan[i].baseFreq,opChan[i].pitch,opChan[i].fixedArp?opChan[i].baseNoteOverride:opChan[i].arpOff,opChan[i].fixedArp,false,2,opChan[i].pitch2,chipClock,CHIP_FREQBASE,11);
+        opChan[i].freq=parent->calcFreq(opChan[i].baseFreq,opChan[i].pitch,opChan[i].fixedArp?opChan[i].baseNoteOverride:opChan[i].arpOff,opChan[i].fixedArp,false,2,opChan[i].pitch2,chipClock,CHIP_FREQBASE,11,chan[extChanOffs].state.block);
       } else {
         int fNum=parent->calcFreq(opChan[i].baseFreq&0x7ff,opChan[i].pitch,opChan[i].fixedArp?opChan[i].baseNoteOverride:opChan[i].arpOff,opChan[i].fixedArp,false,2,opChan[i].pitch2);
         int block=(opChan[i].baseFreq&0xf800)>>11;
diff --git a/src/engine/platform/opl.cpp b/src/engine/platform/opl.cpp
index 1204615dc..5894ee98c 100644
--- a/src/engine/platform/opl.cpp
+++ b/src/engine/platform/opl.cpp
@@ -19,6 +19,7 @@
 
 #include "opl.h"
 #include "../engine.h"
+#include "../bsr.h"
 #include "../../ta-log.h"
 #include <string.h>
 #include <math.h>
@@ -1386,39 +1387,12 @@ void DivPlatformOPL::tick(bool sysTick) {
         double off=(s->centerRate>=1)?((double)s->centerRate/8363.0):1.0;
         chan[i].freq=(int)(off*parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,2,chan[i].pitch2,chipClock,(524288*768)));
         if (chan[i].freq<0x400) chan[i].freq=0x400;
-        if (chan[i].freq>0x3ffffff) chan[i].freq=0x3ffffff;
-        if (chan[i].freq>=0x2000000) {
+        chan[i].freqH=0;
+        if (chan[i].freq>0x3ffffff) {
+          chan[i].freq=0x3ffffff;
           chan[i].freqH=15;
-        } else if (chan[i].freq>=0x1000000) {
-          chan[i].freqH=14;
-        } else if (chan[i].freq>=0x800000) {
-          chan[i].freqH=13;
-        } else if (chan[i].freq>=0x400000) {
-          chan[i].freqH=12;
-        } else if (chan[i].freq>=0x200000) {
-          chan[i].freqH=11;
-        } else if (chan[i].freq>=0x100000) {
-          chan[i].freqH=10;
-        } else if (chan[i].freq>=0x80000) {
-          chan[i].freqH=9;
-        } else if (chan[i].freq>=0x40000) {
-          chan[i].freqH=8;
-        } else if (chan[i].freq>=0x20000) {
-          chan[i].freqH=7;
-        } else if (chan[i].freq>=0x10000) {
-          chan[i].freqH=6;
-        } else if (chan[i].freq>=0x8000) {
-          chan[i].freqH=5;
-        } else if (chan[i].freq>=0x4000) {
-          chan[i].freqH=4;
-        } else if (chan[i].freq>=0x2000) {
-          chan[i].freqH=3;
-        } else if (chan[i].freq>=0x1000) {
-          chan[i].freqH=2;
         } else if (chan[i].freq>=0x800) {
-          chan[i].freqH=1;
-        } else {
-          chan[i].freqH=0;
+          chan[i].freqH=bsr32(chan[i].freq)-11;
         }
         chan[i].freqL=(chan[i].freq>>chan[i].freqH)&0x3ff;
         chan[i].freqH=8^chan[i].freqH;
@@ -1459,11 +1433,16 @@ void DivPlatformOPL::tick(bool sysTick) {
       }
     } else {
       if (chan[i].freqChanged) {
-        chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,octave(chan[i].baseFreq)*2,chan[i].pitch2,chipClock,CHIP_FREQBASE);
+        int mul=2;
+        int fixedBlock=chan[i].state.block;
+        if (parent->song.linearPitch!=2) {
+          mul=octave(chan[i].baseFreq,fixedBlock)*2;
+        }
+        chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,mul,chan[i].pitch2,chipClock,CHIP_FREQBASE);
         if (chan[i].fixedFreq>0) chan[i].freq=chan[i].fixedFreq;
         if (chan[i].freq<0) chan[i].freq=0;
         if (chan[i].freq>131071) chan[i].freq=131071;
-        int freqt=toFreq(chan[i].freq);
+        int freqt=toFreq(chan[i].freq,fixedBlock);
         chan[i].freqH=freqt>>8;
         chan[i].freqL=freqt&0xff;
         immWrite(chanMap[i]+ADDR_FREQ,chan[i].freqL);
@@ -1527,45 +1506,26 @@ void DivPlatformOPL::tick(bool sysTick) {
 
 #define OPLL_C_NUM 686
 
-int DivPlatformOPL::octave(int freq) {
-  if (freq>=OPLL_C_NUM*64) {
-    return 128;
-  } else if (freq>=OPLL_C_NUM*32) {
-    return 64;
-  } else if (freq>=OPLL_C_NUM*16) {
-    return 32;
-  } else if (freq>=OPLL_C_NUM*8) {
-    return 16;
-  } else if (freq>=OPLL_C_NUM*4) {
-    return 8;
-  } else if (freq>=OPLL_C_NUM*2) {
-    return 4;
-  } else if (freq>=OPLL_C_NUM) {
-    return 2;
-  } else {
-    return 1;
+int DivPlatformOPL::octave(int freq, int fixedBlock) {
+  if (fixedBlock>0) {
+    return 1<<(fixedBlock-1);
   }
-  return 1;
+  freq/=OPLL_C_NUM;
+  if (freq==0) return 1;
+  return 1<<bsr(freq);
 }
 
-int DivPlatformOPL::toFreq(int freq) {
-  if (freq>=OPLL_C_NUM*64) {
-    return 0x1c00|((freq>>7)&0x3ff);
-  } else if (freq>=OPLL_C_NUM*32) {
-    return 0x1800|((freq>>6)&0x3ff);
-  } else if (freq>=OPLL_C_NUM*16) {
-    return 0x1400|((freq>>5)&0x3ff);
-  } else if (freq>=OPLL_C_NUM*8) {
-    return 0x1000|((freq>>4)&0x3ff);
-  } else if (freq>=OPLL_C_NUM*4) {
-    return 0xc00|((freq>>3)&0x3ff);
-  } else if (freq>=OPLL_C_NUM*2) {
-    return 0x800|((freq>>2)&0x3ff);
-  } else if (freq>=OPLL_C_NUM) {
-    return 0x400|((freq>>1)&0x3ff);
+int DivPlatformOPL::toFreq(int freq, int fixedBlock) {
+  int block=0;
+  if (fixedBlock>0) {
+    block=fixedBlock-1;
   } else {
-    return freq&0x3ff;
+    block=freq/OPLL_C_NUM;
+    if (block>0) block=bsr(block);
   }
+  freq>>=block;
+  if (freq>0x3ff) freq=0x3ff;
+  return (block<<10)|freq;
 }
 
 void DivPlatformOPL::muteChannel(int ch, bool mute) {
@@ -2075,21 +2035,27 @@ int DivPlatformOPL::dispatch(DivCommand c) {
       int destFreq=(c.chan==adpcmChan)?(NOTE_ADPCMB(c.value2)):(NOTE_FREQUENCY(c.value2));
       int newFreq;
       bool return2=false;
+      int mul=1;
+      int fixedBlock=0;
+      if (parent->song.linearPitch!=2) {
+        fixedBlock=chan[c.chan].state.block;
+        mul=octave(chan[c.chan].baseFreq,fixedBlock);
+      }
       if (destFreq>chan[c.chan].baseFreq) {
-        newFreq=chan[c.chan].baseFreq+c.value*((parent->song.linearPitch==2)?1:octave(chan[c.chan].baseFreq));
+        newFreq=chan[c.chan].baseFreq+c.value*mul;
         if (newFreq>=destFreq) {
           newFreq=destFreq;
           return2=true;
         }
       } else {
-        newFreq=chan[c.chan].baseFreq-c.value*((parent->song.linearPitch==2)?1:octave(chan[c.chan].baseFreq));
+        newFreq=chan[c.chan].baseFreq-c.value*mul;
         if (newFreq<=destFreq) {
           newFreq=destFreq;
           return2=true;
         }
       }
       if (!chan[c.chan].portaPause && parent->song.linearPitch!=2) {
-        if (octave(chan[c.chan].baseFreq)!=octave(newFreq)) {
+        if (mul!=octave(newFreq,fixedBlock)) {
           chan[c.chan].portaPause=true;
           break;
         }
diff --git a/src/engine/platform/opl.h b/src/engine/platform/opl.h
index f976d0468..39b544daa 100644
--- a/src/engine/platform/opl.h
+++ b/src/engine/platform/opl.h
@@ -169,8 +169,8 @@ class DivPlatformOPL: public DivDispatch {
 
     DivMemoryComposition memCompo;
 
-    int octave(int freq);
-    int toFreq(int freq);
+    int octave(int freq, int fixedBlock);
+    int toFreq(int freq, int fixedBlock);
     double NOTE_ADPCMB(int note);
     void commitState(int ch, DivInstrument* ins);
 
diff --git a/src/engine/platform/opll.cpp b/src/engine/platform/opll.cpp
index fb3461622..179103916 100644
--- a/src/engine/platform/opll.cpp
+++ b/src/engine/platform/opll.cpp
@@ -19,6 +19,7 @@
 
 #include "opll.h"
 #include "../engine.h"
+#include "../bsr.h"
 #include "../../ta-log.h"
 #include <string.h>
 #include <math.h>
@@ -294,11 +295,16 @@ void DivPlatformOPLL::tick(bool sysTick) {
 
   for (int i=0; i<11; i++) {
     if (chan[i].freqChanged) {
-      chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,octave(chan[i].baseFreq)*2,chan[i].pitch2,chipClock,CHIP_FREQBASE);
+      int mul=2;
+      int fixedBlock=chan[i].state.block;
+      if (parent->song.linearPitch!=2) {
+        mul=octave(chan[i].baseFreq,fixedBlock)*2;
+      }
+      chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,mul,chan[i].pitch2,chipClock,CHIP_FREQBASE);
       if (chan[i].fixedFreq>0 && properDrums) chan[i].freq=chan[i].fixedFreq;
       if (chan[i].freq<0) chan[i].freq=0;
       if (chan[i].freq>65535) chan[i].freq=65535;
-      int freqt=toFreq(chan[i].freq);
+      int freqt=toFreq(chan[i].freq,fixedBlock);
       if (freqt>4095) freqt=4095;
       chan[i].freqL=freqt&0xff;
       if (i>=6 && properDrums && (i<9 || !noTopHatFreq)) {
@@ -351,45 +357,26 @@ void DivPlatformOPLL::tick(bool sysTick) {
 
 #define OPLL_C_NUM 343
 
-int DivPlatformOPLL::octave(int freq) {
-  if (freq>=OPLL_C_NUM*64) {
-    return 128;
-  } else if (freq>=OPLL_C_NUM*32) {
-    return 64;
-  } else if (freq>=OPLL_C_NUM*16) {
-    return 32;
-  } else if (freq>=OPLL_C_NUM*8) {
-    return 16;
-  } else if (freq>=OPLL_C_NUM*4) {
-    return 8;
-  } else if (freq>=OPLL_C_NUM*2) {
-    return 4;
-  } else if (freq>=OPLL_C_NUM) {
-    return 2;
-  } else {
-    return 1;
+int DivPlatformOPLL::octave(int freq, int fixedBlock) {
+  if (fixedBlock>0) {
+    return 1<<(fixedBlock-1);
   }
-  return 1;
+  freq/=OPLL_C_NUM;
+  if (freq==0) return 1;
+  return 1<<bsr(freq);
 }
 
-int DivPlatformOPLL::toFreq(int freq) {
-  if (freq>=OPLL_C_NUM*64) {
-    return 0xe00|((freq>>7)&0x1ff);
-  } else if (freq>=OPLL_C_NUM*32) {
-    return 0xc00|((freq>>6)&0x1ff);
-  } else if (freq>=OPLL_C_NUM*16) {
-    return 0xa00|((freq>>5)&0x1ff);
-  } else if (freq>=OPLL_C_NUM*8) {
-    return 0x800|((freq>>4)&0x1ff);
-  } else if (freq>=OPLL_C_NUM*4) {
-    return 0x600|((freq>>3)&0x1ff);
-  } else if (freq>=OPLL_C_NUM*2) {
-    return 0x400|((freq>>2)&0x1ff);
-  } else if (freq>=OPLL_C_NUM) {
-    return 0x200|((freq>>1)&0x1ff);
+int DivPlatformOPLL::toFreq(int freq, int fixedBlock) {
+  int block=0;
+  if (fixedBlock>0) {
+    block=fixedBlock-1;
   } else {
-    return freq&0x1ff;
+    block=freq/OPLL_C_NUM;
+    if (block>0) block=bsr(block);
   }
+  freq>>=block;
+  if (freq>0x1ff) freq=0x1ff;
+  return (block<<9)|freq;
 }
 
 void DivPlatformOPLL::muteChannel(int ch, bool mute) {
@@ -650,21 +637,27 @@ int DivPlatformOPLL::dispatch(DivCommand c) {
       int destFreq=NOTE_FREQUENCY(c.value2);
       int newFreq;
       bool return2=false;
+      int mul=1;
+      int fixedBlock=0;
+      if (parent->song.linearPitch!=2) {
+        fixedBlock=chan[c.chan].state.block;
+        mul=octave(chan[c.chan].baseFreq,fixedBlock);
+      }
       if (destFreq>chan[c.chan].baseFreq) {
-        newFreq=chan[c.chan].baseFreq+c.value*((parent->song.linearPitch==2)?1:octave(chan[c.chan].baseFreq));
+        newFreq=chan[c.chan].baseFreq+c.value*mul;
         if (newFreq>=destFreq) {
           newFreq=destFreq;
           return2=true;
         }
       } else {
-        newFreq=chan[c.chan].baseFreq-c.value*((parent->song.linearPitch==2)?1:octave(chan[c.chan].baseFreq));
+        newFreq=chan[c.chan].baseFreq-c.value*mul;
         if (newFreq<=destFreq) {
           newFreq=destFreq;
           return2=true;
         }
       }
       /*if (!chan[c.chan].portaPause) {
-        if (octave(chan[c.chan].baseFreq)!=octave(newFreq)) {
+        if (mul!=octave(newFreq,fixedBlock)) {
           chan[c.chan].portaPause=true;
           break;
         }
diff --git a/src/engine/platform/opll.h b/src/engine/platform/opll.h
index b1f6e56ac..58d2538b6 100644
--- a/src/engine/platform/opll.h
+++ b/src/engine/platform/opll.h
@@ -80,8 +80,8 @@ class DivPlatformOPLL: public DivDispatch {
     short oldWrites[256];
     short pendingWrites[256];
 
-    int octave(int freq);
-    int toFreq(int freq);
+    int octave(int freq, int fixedBlock);
+    int toFreq(int freq, int fixedBlock);
     void commitState(int ch, DivInstrument* ins);
     void switchMode(bool mode);
 
diff --git a/src/engine/platform/saa.cpp b/src/engine/platform/saa.cpp
index f1e033b75..4f22cadde 100644
--- a/src/engine/platform/saa.cpp
+++ b/src/engine/platform/saa.cpp
@@ -19,6 +19,7 @@
 
 #include "saa.h"
 #include "../engine.h"
+#include "../bsr.h"
 #include "sound/saa1099.h"
 #include <string.h>
 #include <math.h>
@@ -155,22 +156,9 @@ void DivPlatformSAA1099::tick(bool sysTick) {
     if (chan[i].freqChanged || chan[i].keyOn || chan[i].keyOff) {
       chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,true,0,chan[i].pitch2,chipClock,CHIP_DIVIDER);
       if (chan[i].freq>65535) chan[i].freq=65535;
-      if (chan[i].freq>=32768) {
-        chan[i].freqH=7;
-      } else if (chan[i].freq>=16384) {
-        chan[i].freqH=6;
-      } else if (chan[i].freq>=8192) {
-        chan[i].freqH=5;
-      } else if (chan[i].freq>=4096) {
-        chan[i].freqH=4;
-      } else if (chan[i].freq>=2048) {
-        chan[i].freqH=3;
-      } else if (chan[i].freq>=1024) {
-        chan[i].freqH=2;
-      } else if (chan[i].freq>=512) {
-        chan[i].freqH=1;
-      } else {
-        chan[i].freqH=0;
+      chan[i].freqH=0;
+      if (chan[i].freq>511) {
+        chan[i].freqH=bsr((unsigned short)chan[i].freq)-9;
       }
       chan[i].freqL=0xff-(chan[i].freq>>chan[i].freqH);
       chan[i].freqH=7-chan[i].freqH;
diff --git a/src/engine/platform/ym2203.cpp b/src/engine/platform/ym2203.cpp
index 58044e12d..6ddfbfdf5 100644
--- a/src/engine/platform/ym2203.cpp
+++ b/src/engine/platform/ym2203.cpp
@@ -503,7 +503,7 @@ void DivPlatformYM2203::tick(bool sysTick) {
       chan[i].handleArp();
     } else if (chan[i].std.arp.had) {
       if (!chan[i].inPorta) {
-        chan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(chan[i].note,chan[i].std.arp.val),11);
+        chan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(chan[i].note,chan[i].std.arp.val),11,chan[i].state.block);
       }
       chan[i].freqChanged=true;
     }
@@ -638,7 +638,7 @@ void DivPlatformYM2203::tick(bool sysTick) {
     if (i==2 && extMode) continue;
     if (chan[i].freqChanged) {
       if (parent->song.linearPitch==2) {
-        chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,4,chan[i].pitch2,chipClock,CHIP_FREQBASE,11);
+        chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,4,chan[i].pitch2,chipClock,CHIP_FREQBASE,11,chan[i].state.block);
       } else {
         int fNum=parent->calcFreq(chan[i].baseFreq&0x7ff,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,4,chan[i].pitch2);
         int block=(chan[i].baseFreq&0xf800)>>11;
@@ -760,7 +760,7 @@ int DivPlatformYM2203::dispatch(DivCommand c) {
       chan[c.chan].insChanged=false;
 
       if (c.value!=DIV_NOTE_NULL) {
-        chan[c.chan].baseFreq=NOTE_FNUM_BLOCK(c.value,11);
+        chan[c.chan].baseFreq=NOTE_FNUM_BLOCK(c.value,11,chan[c.chan].state.block);
         chan[c.chan].portaPause=false;
         chan[c.chan].freqChanged=true;
         chan[c.chan].note=c.value;
@@ -844,7 +844,7 @@ int DivPlatformYM2203::dispatch(DivCommand c) {
         break;
       }
       if (c.chan>(psgChanOffs-1) || parent->song.linearPitch==2) { // PSG
-        int destFreq=NOTE_FNUM_BLOCK(c.value2,11);
+        int destFreq=NOTE_FNUM_BLOCK(c.value2,11,chan[c.chan].state.block);
         bool return2=false;
         if (destFreq>chan[c.chan].baseFreq) {
           chan[c.chan].baseFreq+=c.value;
@@ -866,7 +866,7 @@ int DivPlatformYM2203::dispatch(DivCommand c) {
         }
         break;
       }
-      PLEASE_HELP_ME(chan[c.chan]);
+      PLEASE_HELP_ME(chan[c.chan],chan[c.chan].state.block);
       break;
     }
     case DIV_CMD_LEGATO: {
@@ -878,7 +878,7 @@ int DivPlatformYM2203::dispatch(DivCommand c) {
         commitState(c.chan,ins);
         chan[c.chan].insChanged=false;
       }
-      chan[c.chan].baseFreq=NOTE_FNUM_BLOCK(c.value,11);
+      chan[c.chan].baseFreq=NOTE_FNUM_BLOCK(c.value,11,chan[c.chan].state.block);
       chan[c.chan].freqChanged=true;
       break;
     }
diff --git a/src/engine/platform/ym2203ext.cpp b/src/engine/platform/ym2203ext.cpp
index eeae96957..c4b392880 100644
--- a/src/engine/platform/ym2203ext.cpp
+++ b/src/engine/platform/ym2203ext.cpp
@@ -89,7 +89,7 @@ int DivPlatformYM2203Ext::dispatch(DivCommand c) {
       opChan[ch].insChanged=false;
 
       if (c.value!=DIV_NOTE_NULL) {
-        opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11);
+        opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11,chan[extChanOffs].state.block);
         opChan[ch].portaPause=false;
         opChan[ch].note=c.value;
         opChan[ch].freqChanged=true;
@@ -168,7 +168,7 @@ int DivPlatformYM2203Ext::dispatch(DivCommand c) {
         }
         break;
       }
-      PLEASE_HELP_ME(opChan[ch]);
+      PLEASE_HELP_ME(opChan[ch],chan[extChanOffs].state.block);
       break;
     }
     case DIV_CMD_LEGATO: {
@@ -177,7 +177,7 @@ int DivPlatformYM2203Ext::dispatch(DivCommand c) {
         commitStateExt(ch,ins);
         opChan[ch].insChanged=false;
       }
-      opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11);
+      opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11,chan[extChanOffs].state.block);
       opChan[ch].freqChanged=true;
       break;
     }
@@ -444,7 +444,7 @@ void DivPlatformYM2203Ext::tick(bool sysTick) {
 
     if (opChan[i].std.arp.had) {
       if (!opChan[i].inPorta) {
-        opChan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(opChan[i].note,opChan[i].std.arp.val),11);
+        opChan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(opChan[i].note,opChan[i].std.arp.val),11,chan[extChanOffs].state.block);
       }
       opChan[i].freqChanged=true;
     }
@@ -543,7 +543,7 @@ void DivPlatformYM2203Ext::tick(bool sysTick) {
   if (extMode) for (int i=0; i<4; i++) {
     if (opChan[i].freqChanged) {
       if (parent->song.linearPitch==2) {
-        opChan[i].freq=parent->calcFreq(opChan[i].baseFreq,opChan[i].pitch,opChan[i].fixedArp?opChan[i].baseNoteOverride:opChan[i].arpOff,opChan[i].fixedArp,false,4,opChan[i].pitch2,chipClock,CHIP_FREQBASE,11);
+        opChan[i].freq=parent->calcFreq(opChan[i].baseFreq,opChan[i].pitch,opChan[i].fixedArp?opChan[i].baseNoteOverride:opChan[i].arpOff,opChan[i].fixedArp,false,4,opChan[i].pitch2,chipClock,CHIP_FREQBASE,11,chan[extChanOffs].state.block);
       } else {
         int fNum=parent->calcFreq(opChan[i].baseFreq&0x7ff,opChan[i].pitch,opChan[i].fixedArp?opChan[i].baseNoteOverride:opChan[i].arpOff,opChan[i].fixedArp,false,4,opChan[i].pitch2);
         int block=(opChan[i].baseFreq&0xf800)>>11;
diff --git a/src/engine/platform/ym2608.cpp b/src/engine/platform/ym2608.cpp
index 7e027db29..784bc7fb3 100644
--- a/src/engine/platform/ym2608.cpp
+++ b/src/engine/platform/ym2608.cpp
@@ -284,7 +284,7 @@ double DivPlatformYM2608::NOTE_OPNB(int ch, int note) {
     return NOTE_PERIODIC(note);
   }
   // FM
-  return NOTE_FNUM_BLOCK(note,11);
+  return NOTE_FNUM_BLOCK(note,11,chan[ch].state.block);
 }
 
 double DivPlatformYM2608::NOTE_ADPCMB(int note) {
@@ -719,7 +719,7 @@ void DivPlatformYM2608::tick(bool sysTick) {
       chan[i].handleArp();
     } else if (chan[i].std.arp.had) {
       if (!chan[i].inPorta) {
-        chan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(chan[i].note,chan[i].std.arp.val),11);
+        chan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(chan[i].note,chan[i].std.arp.val),11,chan[i].state.block);
       }
       chan[i].freqChanged=true;
     }
@@ -871,7 +871,7 @@ void DivPlatformYM2608::tick(bool sysTick) {
     if (i==2 && extMode) continue;
     if (chan[i].freqChanged) {
       if (parent->song.linearPitch==2) {
-        chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,4,chan[i].pitch2,chipClock,CHIP_FREQBASE,11);
+        chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,4,chan[i].pitch2,chipClock,CHIP_FREQBASE,11,chan[i].state.block);
       } else {
         int fNum=parent->calcFreq(chan[i].baseFreq&0x7ff,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,4,chan[i].pitch2);
         int block=(chan[i].baseFreq&0xf800)>>11;
@@ -1233,7 +1233,7 @@ int DivPlatformYM2608::dispatch(DivCommand c) {
       chan[c.chan].insChanged=false;
 
       if (c.value!=DIV_NOTE_NULL) {
-        chan[c.chan].baseFreq=NOTE_FNUM_BLOCK(c.value,11);
+        chan[c.chan].baseFreq=NOTE_FNUM_BLOCK(c.value,11,chan[c.chan].state.block);
         chan[c.chan].portaPause=false;
         chan[c.chan].freqChanged=true;
         chan[c.chan].note=c.value;
@@ -1372,7 +1372,7 @@ int DivPlatformYM2608::dispatch(DivCommand c) {
         }
         break;
       }
-      PLEASE_HELP_ME(chan[c.chan]);
+      PLEASE_HELP_ME(chan[c.chan],chan[c.chan].state.block);
       break;
     }
     case DIV_CMD_SAMPLE_BANK:
diff --git a/src/engine/platform/ym2608ext.cpp b/src/engine/platform/ym2608ext.cpp
index 15038de14..8a8784af8 100644
--- a/src/engine/platform/ym2608ext.cpp
+++ b/src/engine/platform/ym2608ext.cpp
@@ -93,7 +93,7 @@ int DivPlatformYM2608Ext::dispatch(DivCommand c) {
       opChan[ch].insChanged=false;
 
       if (c.value!=DIV_NOTE_NULL) {
-        opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11);
+        opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11,chan[extChanOffs].state.block);
         opChan[ch].portaPause=false;
         opChan[ch].note=c.value;
         opChan[ch].freqChanged=true;
@@ -188,7 +188,7 @@ int DivPlatformYM2608Ext::dispatch(DivCommand c) {
         }
         break;
       }
-      PLEASE_HELP_ME(opChan[ch]);
+      PLEASE_HELP_ME(opChan[ch],chan[extChanOffs].state.block);
       break;
     }
     case DIV_CMD_LEGATO: {
@@ -197,7 +197,7 @@ int DivPlatformYM2608Ext::dispatch(DivCommand c) {
         commitStateExt(ch,ins);
         opChan[ch].insChanged=false;
       }
-      opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11);
+      opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11,chan[extChanOffs].state.block);
       opChan[ch].freqChanged=true;
       break;
     }
@@ -472,7 +472,7 @@ void DivPlatformYM2608Ext::tick(bool sysTick) {
 
     if (opChan[i].std.arp.had) {
       if (!opChan[i].inPorta) {
-        opChan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(opChan[i].note,opChan[i].std.arp.val),11);
+        opChan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(opChan[i].note,opChan[i].std.arp.val),11,chan[extChanOffs].state.block);
       }
       opChan[i].freqChanged=true;
     }
@@ -594,7 +594,7 @@ void DivPlatformYM2608Ext::tick(bool sysTick) {
   if (extMode) for (int i=0; i<4; i++) {
     if (opChan[i].freqChanged) {
       if (parent->song.linearPitch==2) {
-        opChan[i].freq=parent->calcFreq(opChan[i].baseFreq,opChan[i].pitch,opChan[i].fixedArp?opChan[i].baseNoteOverride:opChan[i].arpOff,opChan[i].fixedArp,false,4,opChan[i].pitch2,chipClock,CHIP_FREQBASE,11);
+        opChan[i].freq=parent->calcFreq(opChan[i].baseFreq,opChan[i].pitch,opChan[i].fixedArp?opChan[i].baseNoteOverride:opChan[i].arpOff,opChan[i].fixedArp,false,4,opChan[i].pitch2,chipClock,CHIP_FREQBASE,11,chan[extChanOffs].state.block);
       } else {
         int fNum=parent->calcFreq(opChan[i].baseFreq&0x7ff,opChan[i].pitch,opChan[i].fixedArp?opChan[i].baseNoteOverride:opChan[i].arpOff,opChan[i].fixedArp,false,4,opChan[i].pitch2);
         int block=(opChan[i].baseFreq&0xf800)>>11;
diff --git a/src/engine/platform/ym2610.cpp b/src/engine/platform/ym2610.cpp
index afad156ce..3c1d39700 100644
--- a/src/engine/platform/ym2610.cpp
+++ b/src/engine/platform/ym2610.cpp
@@ -647,7 +647,7 @@ void DivPlatformYM2610::tick(bool sysTick) {
       chan[i].handleArp();
     } else if (chan[i].std.arp.had) {
       if (!chan[i].inPorta) {
-        chan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(chan[i].note,chan[i].std.arp.val),11);
+        chan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(chan[i].note,chan[i].std.arp.val),11,chan[i].state.block);
       }
       chan[i].freqChanged=true;
     }
@@ -799,7 +799,7 @@ void DivPlatformYM2610::tick(bool sysTick) {
     if (i==1 && extMode) continue;
     if (chan[i].freqChanged) {
       if (parent->song.linearPitch==2) {
-        chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,4,chan[i].pitch2,chipClock,CHIP_FREQBASE,11);
+        chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,4,chan[i].pitch2,chipClock,CHIP_FREQBASE,11,chan[i].state.block);
       } else {
         int fNum=parent->calcFreq(chan[i].baseFreq&0x7ff,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,4,chan[i].pitch2,chipClock,CHIP_FREQBASE,11);
         int block=(chan[i].baseFreq&0xf800)>>11;
@@ -1200,7 +1200,7 @@ int DivPlatformYM2610::dispatch(DivCommand c) {
       chan[c.chan].insChanged=false;
 
       if (c.value!=DIV_NOTE_NULL) {
-        chan[c.chan].baseFreq=NOTE_FNUM_BLOCK(c.value,11);
+        chan[c.chan].baseFreq=NOTE_FNUM_BLOCK(c.value,11,chan[c.chan].state.block);
         chan[c.chan].portaPause=false;
         chan[c.chan].freqChanged=true;
         chan[c.chan].note=c.value;
@@ -1339,7 +1339,7 @@ int DivPlatformYM2610::dispatch(DivCommand c) {
         }
         break;
       }
-      PLEASE_HELP_ME(chan[c.chan]);
+      PLEASE_HELP_ME(chan[c.chan],chan[c.chan].state.block);
       break;
     }
     case DIV_CMD_SAMPLE_BANK:
diff --git a/src/engine/platform/ym2610b.cpp b/src/engine/platform/ym2610b.cpp
index 9874e7da1..026ad1f3f 100644
--- a/src/engine/platform/ym2610b.cpp
+++ b/src/engine/platform/ym2610b.cpp
@@ -715,7 +715,7 @@ void DivPlatformYM2610B::tick(bool sysTick) {
       chan[i].handleArp();
     } else if (chan[i].std.arp.had) {
       if (!chan[i].inPorta) {
-        chan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(chan[i].note,chan[i].std.arp.val),11);
+        chan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(chan[i].note,chan[i].std.arp.val),11,chan[i].state.block);
       }
       chan[i].freqChanged=true;
     }
@@ -867,7 +867,7 @@ void DivPlatformYM2610B::tick(bool sysTick) {
     if (i==2 && extMode) continue;
     if (chan[i].freqChanged) {
       if (parent->song.linearPitch==2) {
-        chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,4,chan[i].pitch2,chipClock,CHIP_FREQBASE,11);
+        chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,4,chan[i].pitch2,chipClock,CHIP_FREQBASE,11,chan[i].state.block);
       } else {
         int fNum=parent->calcFreq(chan[i].baseFreq&0x7ff,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,4,chan[i].pitch2);
         int block=(chan[i].baseFreq&0xf800)>>11;
@@ -1268,7 +1268,7 @@ int DivPlatformYM2610B::dispatch(DivCommand c) {
       chan[c.chan].insChanged=false;
 
       if (c.value!=DIV_NOTE_NULL) {
-        chan[c.chan].baseFreq=NOTE_FNUM_BLOCK(c.value,11);
+        chan[c.chan].baseFreq=NOTE_FNUM_BLOCK(c.value,11,chan[c.chan].state.block);
         chan[c.chan].portaPause=false;
         chan[c.chan].freqChanged=true;
         chan[c.chan].note=c.value;
@@ -1407,7 +1407,7 @@ int DivPlatformYM2610B::dispatch(DivCommand c) {
         }
         break;
       }
-      PLEASE_HELP_ME(chan[c.chan]);
+      PLEASE_HELP_ME(chan[c.chan],chan[c.chan].state.block);
       break;
     }
     case DIV_CMD_SAMPLE_BANK:
diff --git a/src/engine/platform/ym2610bext.cpp b/src/engine/platform/ym2610bext.cpp
index 035c87cf7..4988e1b6c 100644
--- a/src/engine/platform/ym2610bext.cpp
+++ b/src/engine/platform/ym2610bext.cpp
@@ -89,7 +89,7 @@ int DivPlatformYM2610BExt::dispatch(DivCommand c) {
       opChan[ch].insChanged=false;
 
       if (c.value!=DIV_NOTE_NULL) {
-        opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11);
+        opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11,chan[extChanOffs].state.block);
         opChan[ch].portaPause=false;
         opChan[ch].note=c.value;
         opChan[ch].freqChanged=true;
@@ -184,7 +184,7 @@ int DivPlatformYM2610BExt::dispatch(DivCommand c) {
         }
         break;
       }
-      PLEASE_HELP_ME(opChan[ch]);
+      PLEASE_HELP_ME(opChan[ch],chan[extChanOffs].state.block);
       break;
     }
     case DIV_CMD_LEGATO: {
@@ -193,7 +193,7 @@ int DivPlatformYM2610BExt::dispatch(DivCommand c) {
         commitStateExt(ch,ins);
         opChan[ch].insChanged=false;
       }
-      opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11);
+      opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11,chan[extChanOffs].state.block);
       opChan[ch].freqChanged=true;
       break;
     }
@@ -465,7 +465,7 @@ void DivPlatformYM2610BExt::tick(bool sysTick) {
 
     if (opChan[i].std.arp.had) {
       if (!opChan[i].inPorta) {
-        opChan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(opChan[i].note,opChan[i].std.arp.val),11);
+        opChan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(opChan[i].note,opChan[i].std.arp.val),11,chan[extChanOffs].state.block);
       }
       opChan[i].freqChanged=true;
     }
@@ -586,7 +586,7 @@ void DivPlatformYM2610BExt::tick(bool sysTick) {
   if (extMode) for (int i=0; i<4; i++) {
     if (opChan[i].freqChanged) {
       if (parent->song.linearPitch==2) {
-        opChan[i].freq=parent->calcFreq(opChan[i].baseFreq,opChan[i].pitch,opChan[i].fixedArp?opChan[i].baseNoteOverride:opChan[i].arpOff,opChan[i].fixedArp,false,4,opChan[i].pitch2,chipClock,CHIP_FREQBASE,11);
+        opChan[i].freq=parent->calcFreq(opChan[i].baseFreq,opChan[i].pitch,opChan[i].fixedArp?opChan[i].baseNoteOverride:opChan[i].arpOff,opChan[i].fixedArp,false,4,opChan[i].pitch2,chipClock,CHIP_FREQBASE,11,chan[extChanOffs].state.block);
       } else {
         int fNum=parent->calcFreq(opChan[i].baseFreq&0x7ff,opChan[i].pitch,opChan[i].fixedArp?opChan[i].baseNoteOverride:opChan[i].arpOff,opChan[i].fixedArp,false,4,opChan[i].pitch2);
         int block=(opChan[i].baseFreq&0xf800)>>11;
diff --git a/src/engine/platform/ym2610ext.cpp b/src/engine/platform/ym2610ext.cpp
index c4472f597..a3b2455bc 100644
--- a/src/engine/platform/ym2610ext.cpp
+++ b/src/engine/platform/ym2610ext.cpp
@@ -89,7 +89,7 @@ int DivPlatformYM2610Ext::dispatch(DivCommand c) {
       opChan[ch].insChanged=false;
 
       if (c.value!=DIV_NOTE_NULL) {
-        opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11);
+        opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11,chan[extChanOffs].state.block);
         opChan[ch].portaPause=false;
         opChan[ch].note=c.value;
         opChan[ch].freqChanged=true;
@@ -184,7 +184,7 @@ int DivPlatformYM2610Ext::dispatch(DivCommand c) {
         }
         break;
       }
-      PLEASE_HELP_ME(opChan[ch]);
+      PLEASE_HELP_ME(opChan[ch],chan[extChanOffs].state.block);
       break;
     }
     case DIV_CMD_LEGATO: {
@@ -193,7 +193,7 @@ int DivPlatformYM2610Ext::dispatch(DivCommand c) {
         commitStateExt(ch,ins);
         opChan[ch].insChanged=false;
       }
-      opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11);
+      opChan[ch].baseFreq=NOTE_FNUM_BLOCK(c.value,11,chan[extChanOffs].state.block);
       opChan[ch].freqChanged=true;
       break;
     }
@@ -465,7 +465,7 @@ void DivPlatformYM2610Ext::tick(bool sysTick) {
 
     if (opChan[i].std.arp.had) {
       if (!opChan[i].inPorta) {
-        opChan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(opChan[i].note,opChan[i].std.arp.val),11);
+        opChan[i].baseFreq=NOTE_FNUM_BLOCK(parent->calcArp(opChan[i].note,opChan[i].std.arp.val),11,chan[extChanOffs].state.block);
       }
       opChan[i].freqChanged=true;
     }
@@ -586,7 +586,7 @@ void DivPlatformYM2610Ext::tick(bool sysTick) {
   if (extMode) for (int i=0; i<4; i++) {
     if (opChan[i].freqChanged) {
       if (parent->song.linearPitch==2) {
-        opChan[i].freq=parent->calcFreq(opChan[i].baseFreq,opChan[i].pitch,opChan[i].fixedArp?opChan[i].baseNoteOverride:opChan[i].arpOff,opChan[i].fixedArp,false,4,opChan[i].pitch2,chipClock,CHIP_FREQBASE,11);
+        opChan[i].freq=parent->calcFreq(opChan[i].baseFreq,opChan[i].pitch,opChan[i].fixedArp?opChan[i].baseNoteOverride:opChan[i].arpOff,opChan[i].fixedArp,false,4,opChan[i].pitch2,chipClock,CHIP_FREQBASE,11,chan[extChanOffs].state.block);
       } else {
         int fNum=parent->calcFreq(opChan[i].baseFreq&0x7ff,opChan[i].pitch,opChan[i].fixedArp?opChan[i].baseNoteOverride:opChan[i].arpOff,opChan[i].fixedArp,false,4,opChan[i].pitch2);
         int block=(opChan[i].baseFreq&0xf800)>>11;
diff --git a/src/engine/platform/ym2610shared.h b/src/engine/platform/ym2610shared.h
index ea9d66031..d5e12df10 100644
--- a/src/engine/platform/ym2610shared.h
+++ b/src/engine/platform/ym2610shared.h
@@ -97,7 +97,7 @@ class DivPlatformYM2610Base: public DivPlatformOPN {
         return NOTE_PERIODIC(note);
       }
       // FM
-      return NOTE_FNUM_BLOCK(note,11);
+      return NOTE_FNUM_BLOCK(note,11,chan[ch].state.block);
     }
     double NOTE_ADPCMB(int note) {
       if (chan[adpcmBChanOffs].sample>=0 && chan[adpcmBChanOffs].sample<parent->song.sampleLen) {
diff --git a/src/gui/fmPreview.cpp b/src/gui/fmPreview.cpp
index 4e11137b9..fc4eb0c6c 100644
--- a/src/gui/fmPreview.cpp
+++ b/src/gui/fmPreview.cpp
@@ -27,6 +27,7 @@ extern "C" {
 #include "../../extern/Nuked-OPLL/opll.h"
 }
 #include "../engine/platform/sound/ymfm/ymfm_opz.h"
+#include "../engine/bsr.h"
 
 #define OPN_WRITE(addr,val) \
   OPN2_Write((ym3438_t*)fmPreviewOPN,0,(addr)); \
@@ -388,9 +389,9 @@ void FurnaceGUI::renderFMPreviewESFM(const DivInstrumentFM& params, const DivIns
         double fbase=(mult0?2048.0:1024.0)*pow(2.0,(float)offset/(128.0*12.0));
         int bf=round(fbase);
         int block=0;
-        while (bf>0x3ff) {
-          bf>>=1;
-          block++;
+        if (bf>0x3ff) {
+          block=bsr32(bf)-10;
+          bf>>=block;
         }
         freqL=bf&0xff;
         freqH=((block&7)<<2)|((bf>>8)&3);
diff --git a/src/gui/insEdit.cpp b/src/gui/insEdit.cpp
index 1879d7fd9..f7d2bb38c 100644
--- a/src/gui/insEdit.cpp
+++ b/src/gui/insEdit.cpp
@@ -49,10 +49,10 @@ const char* ssgEnvTypes[8]={
   _N("Up DOWN")
 };
 
-const char* fmParamNames[3][32]={
-  {_N("Algorithm"), _N("Feedback"), _N("LFO > Freq"), _N("LFO > Amp"), _N("Attack"), _N("Decay"), _N("Decay 2"), _N("Release"), _N("Sustain"), _N("Level"), _N("EnvScale"), _N("Multiplier"), _N("Detune"), _N("Detune 2"), _N("SSG-EG"), _N("AM"), _N("AM Depth"), _N("Vibrato Depth"), _N("Sustained"), _N("Sustained"), _N("Level Scaling"), _N("Sustain"), _N("Vibrato"), _N("Waveform"), _N("Scale Rate"), _N("OP2 Half Sine"), _N("OP1 Half Sine"), _N("EnvShift"), _N("Reverb"), _N("Fine"), _N("LFO2 > Freq"), _N("LFO2 > Amp")},
-  {"ALG", "FB", "FMS/PMS", "AMS", "AR", "DR", "SR", "RR", "SL", "TL", "KS", "MULT", "DT", "DT2", "SSG-EG", "AM", "AMD", "FMD", "EGT", "EGT", "KSL", "SUS", "VIB", "WS", "KSR", "DC", "DM", "EGS", "REV", "Fine", "FMS/PMS2", "AMS2"},
-  {"ALG", "FB", "FMS/PMS", "AMS", "AR", "DR", "D2R", "RR", "SL", "TL", "RS", "MULT", "DT", "DT2", "SSG-EG", "AM", "DAM", "DVB", "EGT", "EGS", "KSL", "SUS", "VIB", "WS", "KSR", "DC", "DM", "EGS", "REV", "Fine", "FMS/PMS2", "AMS2"}
+const char* fmParamNames[3][33]={
+  {_N("Algorithm"), _N("Feedback"), _N("LFO > Freq"), _N("LFO > Amp"), _N("Attack"), _N("Decay"), _N("Decay 2"), _N("Release"), _N("Sustain"), _N("Level"), _N("EnvScale"), _N("Multiplier"), _N("Detune"), _N("Detune 2"), _N("SSG-EG"), _N("AM"), _N("AM Depth"), _N("Vibrato Depth"), _N("Sustained"), _N("Sustained"), _N("Level Scaling"), _N("Sustain"), _N("Vibrato"), _N("Waveform"), _N("Scale Rate"), _N("OP2 Half Sine"), _N("OP1 Half Sine"), _N("EnvShift"), _N("Reverb"), _N("Fine"), _N("LFO2 > Freq"), _N("LFO2 > Amp"), _N("Octave")},
+  {"ALG", "FB", "FMS/PMS", "AMS", "AR", "DR", "SR", "RR", "SL", "TL", "KS", "MULT", "DT", "DT2", "SSG-EG", "AM", "AMD", "FMD", "EGT", "EGT", "KSL", "SUS", "VIB", "WS", "KSR", "DC", "DM", "EGS", "REV", "Fine", "FMS/PMS2", "AMS2", "Block"},
+  {"ALG", "FB", "FMS/PMS", "AMS", "AR", "DR", "D2R", "RR", "SL", "TL", "RS", "MULT", "DT", "DT2", "SSG-EG", "AM", "DAM", "DVB", "EGT", "EGS", "KSL", "SUS", "VIB", "WS", "KSR", "DC", "DM", "EGS", "REV", "Fine", "FMS/PMS2", "AMS2", "Block"}
 };
 
 const char* esfmParamLongNames[9]={
@@ -388,7 +388,8 @@ enum FMParams {
   FM_REV=28,
   FM_FINE=29,
   FM_FMS2=30,
-  FM_AMS2=31
+  FM_AMS2=31,
+  FM_BLOCK=32
 };
 
 enum ESFMParams {
@@ -3909,8 +3910,13 @@ void FurnaceGUI::insTabFM(DivInstrument* ins) {
     }
 
     if (ImGui::BeginTable("fmDetails",3,(ins->type==DIV_INS_ESFM)?ImGuiTableFlags_SizingStretchProp:ImGuiTableFlags_SizingStretchSame)) {
-      ImGui::TableSetupColumn("c0",ImGuiTableColumnFlags_WidthStretch,((ins->type==DIV_INS_ESFM)?0.50f:0.0f));
-      ImGui::TableSetupColumn("c1",ImGuiTableColumnFlags_WidthStretch,((ins->type==DIV_INS_ESFM)?0.15f:0.0f));
+      String blockTxt=_("Automatic");
+      if (ins->fm.block>=1) {
+        blockTxt=fmt::sprintf("%d",ins->fm.block-1);
+      }
+
+      ImGui::TableSetupColumn("c0",ImGuiTableColumnFlags_WidthStretch,((ins->type==DIV_INS_ESFM)?0.40f:0.0f));
+      ImGui::TableSetupColumn("c1",ImGuiTableColumnFlags_WidthStretch,((ins->type==DIV_INS_ESFM)?0.25f:0.0f));
       ImGui::TableSetupColumn("c2",ImGuiTableColumnFlags_WidthStretch,((ins->type==DIV_INS_ESFM)?0.35f:0.0f));
 
       ImGui::TableNextRow();
@@ -3920,6 +3926,9 @@ void FurnaceGUI::insTabFM(DivInstrument* ins) {
           ImGui::TableNextColumn();
           P(CWSliderScalar(FM_NAME(FM_FB),ImGuiDataType_U8,&ins->fm.fb,&_ZERO,&_SEVEN)); rightClickable
           P(CWSliderScalar(FM_NAME(FM_FMS),ImGuiDataType_U8,&ins->fm.fms,&_ZERO,&_SEVEN)); rightClickable
+          if (ins->type==DIV_INS_FM) {
+            P(CWSliderScalar(FM_NAME(FM_BLOCK),ImGuiDataType_U8,&ins->fm.block,&_ZERO,&_EIGHT,blockTxt.c_str())); rightClickable
+          }
           ImGui::TableNextColumn();
           P(CWSliderScalar(FM_NAME(FM_ALG),ImGuiDataType_U8,&ins->fm.alg,&_ZERO,&_SEVEN)); rightClickable
           P(CWSliderScalar(FM_NAME(FM_AMS),ImGuiDataType_U8,&ins->fm.ams,&_ZERO,&_THREE)); rightClickable
@@ -3974,16 +3983,16 @@ void FurnaceGUI::insTabFM(DivInstrument* ins) {
           ImGui::TableNextColumn();
           ins->fm.alg&=algMax;
           P(CWSliderScalar(FM_NAME(FM_FB),ImGuiDataType_U8,&ins->fm.fb,&_ZERO,&_SEVEN)); rightClickable
+          P(CWSliderScalar(FM_NAME(FM_BLOCK),ImGuiDataType_U8,&ins->fm.block,&_ZERO,&_EIGHT,blockTxt.c_str())); rightClickable
+          ImGui::TableNextColumn();
+          P(CWSliderScalar(FM_NAME(FM_ALG),ImGuiDataType_U8,&ins->fm.alg,&_ZERO,&algMax)); rightClickable
           if (ins->type==DIV_INS_OPL) {
             ImGui::BeginDisabled(ins->fm.opllPreset==16);
             if (ImGui::Checkbox("4-op",&fourOp)) { PARAMETER
               ins->fm.ops=fourOp?4:2;
             }
             ImGui::EndDisabled();
-          }
-          ImGui::TableNextColumn();
-          P(CWSliderScalar(FM_NAME(FM_ALG),ImGuiDataType_U8,&ins->fm.alg,&_ZERO,&algMax)); rightClickable
-          if (ins->type==DIV_INS_OPL) {
+            ImGui::SameLine();
             if (ImGui::Checkbox(_("Drums"),&drums)) { PARAMETER
               ins->fm.opllPreset=drums?16:0;
             }
@@ -4008,15 +4017,21 @@ void FurnaceGUI::insTabFM(DivInstrument* ins) {
           ImGui::TableNextColumn();
           ImGui::BeginDisabled(ins->fm.opllPreset!=0);
           P(CWSliderScalar(FM_NAME(FM_FB),ImGuiDataType_U8,&fmOrigin.fb,&_ZERO,&_SEVEN)); rightClickable
-          if (ImGui::Checkbox(FM_NAME(FM_DC),&dc)) { PARAMETER
-            fmOrigin.fms=dc;
-          }
           ImGui::EndDisabled();
+          P(CWSliderScalar(FM_NAME(FM_BLOCK),ImGuiDataType_U8,&ins->fm.block,&_ZERO,&_EIGHT,blockTxt.c_str())); rightClickable
+          if (ins->fm.opllPreset!=0) {
+            ins->fm.op[1].tl&=15;
+            P(CWSliderScalar(_("Volume##TL"),ImGuiDataType_U8,&ins->fm.op[1].tl,&_FIFTEEN,&_ZERO)); rightClickable
+          }
           ImGui::TableNextColumn();
           if (ImGui::Checkbox(FM_NAME(FM_SUS),&sus)) { PARAMETER
             ins->fm.alg=sus;
           }
           ImGui::BeginDisabled(ins->fm.opllPreset!=0);
+          if (ImGui::Checkbox(FM_NAME(FM_DC),&dc)) { PARAMETER
+            fmOrigin.fms=dc;
+          }
+          ImGui::SameLine();
           if (ImGui::Checkbox(FM_NAME(FM_DM),&dm)) { PARAMETER
             fmOrigin.ams=dm;
           }
@@ -4074,6 +4089,7 @@ void FurnaceGUI::insTabFM(DivInstrument* ins) {
           P(CWSliderScalar(ESFM_LONG_NAME(ESFM_NOISE),ImGuiDataType_U8,&ins->esfm.noise,&_ZERO,&_THREE,_(esfmNoiseModeNames[ins->esfm.noise&3]))); rightClickable
           ImGui::TextUnformatted(_(esfmNoiseModeDescriptions[ins->esfm.noise&3]));
           ImGui::TableNextColumn();
+          P(CWSliderScalar(FM_NAME(FM_BLOCK),ImGuiDataType_U8,&ins->fm.block,&_ZERO,&_EIGHT,blockTxt.c_str())); rightClickable
           ImGui::TableNextColumn();
           if (fmPreviewOn) {
             drawFMPreview(ImVec2(ImGui::GetContentRegionAvail().x,48.0*dpiScale));
@@ -4091,6 +4107,9 @@ void FurnaceGUI::insTabFM(DivInstrument* ins) {
       }
       ImGui::EndTable();
     }
+    if (ins->type==DIV_INS_OPLL && ins->fm.opllPreset==16) {
+      ImGui::Text(_("this volume slider only works in compatibility (non-drums) system."));
+    }
 
     if (((ins->type==DIV_INS_OPLL || ins->type==DIV_INS_OPL) && ins->fm.opllPreset==16) || ins->type==DIV_INS_OPL_DRUMS) {
       ins->fm.ops=2;
@@ -4121,12 +4140,6 @@ void FurnaceGUI::insTabFM(DivInstrument* ins) {
     bool willDisplayOps=true;
     if (ins->type==DIV_INS_OPLL && ins->fm.opllPreset!=0) willDisplayOps=false;
     if (!willDisplayOps && ins->type==DIV_INS_OPLL) {
-      ins->fm.op[1].tl&=15;
-      P(CWSliderScalar(_("Volume##TL"),ImGuiDataType_U8,&ins->fm.op[1].tl,&_FIFTEEN,&_ZERO)); rightClickable
-      if (ins->fm.opllPreset==16) {
-        ImGui::Text(_("this volume slider only works in compatibility (non-drums) system."));
-      }
-
       // update OPLL preset preview
       if (ins->fm.opllPreset>0 && ins->fm.opllPreset<16) {
         const opll_patch_t* patchROM=NULL;