diff --git a/src/engine/cmdStream.cpp b/src/engine/cmdStream.cpp
index 41c2c3cc8..6b5d9ee93 100644
--- a/src/engine/cmdStream.cpp
+++ b/src/engine/cmdStream.cpp
@@ -704,7 +704,12 @@ bool DivCSPlayer::init() {
 
   // initialize state
   for (int i=0; i<e->getTotalChannelCount(); i++) {
-    chan[i].volMax=(e->getDispatch(e->song.dispatchOfChan[i])->dispatch(DivCommand(DIV_CMD_GET_VOLMAX,e->song.dispatchChanOfChan[i]))<<8)|0xff;
+    if (e->song.dispatchChanOfChan[i]>=0) {
+      chan[i].volMax=(e->getDispatch(e->song.dispatchOfChan[i])->dispatch(DivCommand(DIV_CMD_GET_VOLMAX,e->song.dispatchChanOfChan[i]))<<8)|0xff;
+    } else {
+      // fallback
+      chan[i].volMax=0xfff;
+    }
     chan[i].volume=chan[i].volMax;
   }
 
diff --git a/src/engine/engine.cpp b/src/engine/engine.cpp
index a27fe8a69..6fd6fef4f 100644
--- a/src/engine/engine.cpp
+++ b/src/engine/engine.cpp
@@ -1536,21 +1536,25 @@ DivChannelState* DivEngine::getChanState(int ch) {
 
 unsigned short DivEngine::getChanPan(int ch) {
   if (ch<0 || ch>=song.chans) return 0;
+  if (song.dispatchChanOfChan[ch]<0) return 0;
   return disCont[song.dispatchOfChan[ch]].dispatch->getPan(song.dispatchChanOfChan[ch]);
 }
 
 void* DivEngine::getDispatchChanState(int ch) {
   if (ch<0 || ch>=song.chans) return NULL;
+  if (song.dispatchChanOfChan[ch]<0) return NULL;
   return disCont[song.dispatchOfChan[ch]].dispatch->getChanState(song.dispatchChanOfChan[ch]);
 }
 
 void DivEngine::getChanPaired(int ch, std::vector<DivChannelPair>& ret) {
   if (ch<0 || ch>=song.chans) return;
+  if (song.dispatchChanOfChan[ch]<0) return;
   disCont[song.dispatchOfChan[ch]].dispatch->getPaired(song.dispatchChanOfChan[ch],ret);
 }
 
 DivChannelModeHints DivEngine::getChanModeHints(int ch) {
   if (ch<0 || ch>=song.chans) return DivChannelModeHints();
+  if (song.dispatchChanOfChan[ch]<0) return DivChannelModeHints();
   return disCont[song.dispatchOfChan[ch]].dispatch->getModeHints(song.dispatchChanOfChan[ch]);
 }
 
@@ -1564,16 +1568,19 @@ unsigned char* DivEngine::getRegisterPool(int sys, int& size, int& depth) {
 
 DivMacroInt* DivEngine::getMacroInt(int chan) {
   if (chan<0 || chan>=song.chans) return NULL;
+  if (song.dispatchChanOfChan[chan]<0) return NULL;
   return disCont[song.dispatchOfChan[chan]].dispatch->getChanMacroInt(song.dispatchChanOfChan[chan]);
 }
 
 DivSamplePos DivEngine::getSamplePos(int chan) {
   if (chan<0 || chan>=song.chans) return DivSamplePos();
+  if (song.dispatchChanOfChan[chan]<0) return DivSamplePos();
   return disCont[song.dispatchOfChan[chan]].dispatch->getSamplePos(song.dispatchChanOfChan[chan]);
 }
 
 DivDispatchOscBuffer* DivEngine::getOscBuffer(int chan) {
   if (chan<0 || chan>=song.chans) return NULL;
+  if (song.dispatchChanOfChan[chan]<0) return NULL;
   return disCont[song.dispatchOfChan[chan]].dispatch->getOscBuffer(song.dispatchChanOfChan[chan]);
 }
 
@@ -2070,6 +2077,7 @@ void DivEngine::stop() {
 
   // reset all chan oscs
   for (int i=0; i<song.chans; i++) {
+    if (song.dispatchChanOfChan[i]<0) continue;
     DivDispatchOscBuffer* buf=disCont[song.dispatchOfChan[i]].dispatch->getOscBuffer(song.dispatchChanOfChan[i]);
     if (buf!=NULL) {
       buf->reset();
@@ -2118,7 +2126,9 @@ void DivEngine::reset() {
   }
   for (int i=0; i<DIV_MAX_CHANS; i++) {
     chan[i]=DivChannelState();
-    if (i<song.chans) chan[i].volMax=(disCont[song.dispatchOfChan[i]].dispatch->dispatch(DivCommand(DIV_CMD_GET_VOLMAX,song.dispatchChanOfChan[i]))<<8)|0xff;
+    if (i<song.chans && song.dispatchChanOfChan[i]>=0) {
+      chan[i].volMax=(disCont[song.dispatchOfChan[i]].dispatch->dispatch(DivCommand(DIV_CMD_GET_VOLMAX,song.dispatchChanOfChan[i]))<<8)|0xff;
+    }
     chan[i].volume=chan[i].volMax;
     if (!song.linearPitch) chan[i].vibratoFine=4;
   }
@@ -2393,6 +2403,7 @@ int DivEngine::mapVelocity(int ch, float vel) {
   if (ch<0) return 0;
   if (ch>=song.chans) return 0;
   if (disCont[song.dispatchOfChan[ch]].dispatch==NULL) return 0;
+  if (song.dispatchChanOfChan[ch]<0) return 0;
   return disCont[song.dispatchOfChan[ch]].dispatch->mapVelocity(song.dispatchChanOfChan[ch],vel);
 }
 
@@ -2400,6 +2411,7 @@ float DivEngine::getGain(int ch, int vol) {
   if (ch<0) return 0;
   if (ch>=song.chans) return 0;
   if (disCont[song.dispatchOfChan[ch]].dispatch==NULL) return 0;
+  if (song.dispatchChanOfChan[ch]<0) return 0;
   return disCont[song.dispatchOfChan[ch]].dispatch->getGain(song.dispatchChanOfChan[ch],vol);
 }
 
@@ -2525,14 +2537,14 @@ void DivEngine::toggleSolo(int chan) {
   if (!solo) {
     for (int i=0; i<song.chans; i++) {
       isMuted[i]=(i!=chan);
-      if (disCont[song.dispatchOfChan[i]].dispatch!=NULL) {
+      if (disCont[song.dispatchOfChan[i]].dispatch!=NULL && song.dispatchChanOfChan[i]>=0) {
         disCont[song.dispatchOfChan[i]].dispatch->muteChannel(song.dispatchChanOfChan[i],isMuted[i]);
       }
     }
   } else {
     for (int i=0; i<song.chans; i++) {
       isMuted[i]=false;
-      if (disCont[song.dispatchOfChan[i]].dispatch!=NULL) {
+      if (disCont[song.dispatchOfChan[i]].dispatch!=NULL && song.dispatchChanOfChan[i]>=0) {
         disCont[song.dispatchOfChan[i]].dispatch->muteChannel(song.dispatchChanOfChan[i],isMuted[i]);
       }
     }
@@ -2543,7 +2555,7 @@ void DivEngine::toggleSolo(int chan) {
 void DivEngine::muteChannel(int chan, bool mute) {
   BUSY_BEGIN;
   isMuted[chan]=mute;
-  if (disCont[song.dispatchOfChan[chan]].dispatch!=NULL) {
+  if (disCont[song.dispatchOfChan[chan]].dispatch!=NULL && song.dispatchChanOfChan[chan]>=0) {
     disCont[song.dispatchOfChan[chan]].dispatch->muteChannel(song.dispatchChanOfChan[chan],isMuted[chan]);
   }
   BUSY_END;
@@ -2553,7 +2565,7 @@ void DivEngine::unmuteAll() {
   BUSY_BEGIN;
   for (int i=0; i<song.chans; i++) {
     isMuted[i]=false;
-    if (disCont[song.dispatchOfChan[i]].dispatch!=NULL) {
+    if (disCont[song.dispatchOfChan[i]].dispatch!=NULL && song.dispatchChanOfChan[i]>=0) {
       disCont[song.dispatchOfChan[i]].dispatch->muteChannel(song.dispatchChanOfChan[i],isMuted[i]);
     }
   }
diff --git a/src/engine/playback.cpp b/src/engine/playback.cpp
index abd79aa6c..f9bda8a9b 100644
--- a/src/engine/playback.cpp
+++ b/src/engine/playback.cpp
@@ -496,6 +496,11 @@ int DivEngine::dispatchCmd(DivCommand c) {
     }
   }
 
+  // don't dispatch if the channel doesn't exist
+  if (song.dispatchChanOfChan[c.dis]<0) {
+    return 0;
+  }
+
   // map the channel to channel of chip
   // c.dis is a copy of c.chan because we'll use it in the next call
   c.chan=song.dispatchChanOfChan[c.dis];
@@ -784,15 +789,10 @@ void DivEngine::processRow(int i, bool afterDelay) {
         chan[i].stopOnOff=false;
       }
       // depending on the system, portamento may still be disabled
-      if (disCont[song.dispatchOfChan[i]].dispatch->keyOffAffectsPorta(song.dispatchChanOfChan[i])) {
+      if (song.dispatchChanOfChan[i]>=0) if (disCont[song.dispatchOfChan[i]].dispatch->keyOffAffectsPorta(song.dispatchChanOfChan[i])) {
         chan[i].portaNote=-1;
         chan[i].portaSpeed=-1;
         dispatchCmd(DivCommand(DIV_CMD_HINT_PORTA,i,CLAMP(chan[i].portaNote,-128,127),MAX(chan[i].portaSpeed,0)));
-        // this here is a now-disabled hack which makes the noise channel also stop when square 3 is
-        /*if (i==2 && song.sysOfChan[i]==DIV_SYSTEM_SMS) {
-          chan[i+1].portaNote=-1;
-          chan[i+1].portaSpeed=-1;
-        }*/
       }
       // another compatibility hack which schedules a second reset later just in case
       chan[i].scheduledSlideReset=true;
@@ -812,14 +812,10 @@ void DivEngine::processRow(int i, bool afterDelay) {
         dispatchCmd(DivCommand(DIV_CMD_HINT_PORTA,i,CLAMP(chan[i].portaNote,-128,127),MAX(chan[i].portaSpeed,0)));
         chan[i].stopOnOff=false;
       }
-      if (disCont[song.dispatchOfChan[i]].dispatch->keyOffAffectsPorta(song.dispatchChanOfChan[i])) {
+      if (song.dispatchChanOfChan[i]>=0) if (disCont[song.dispatchOfChan[i]].dispatch->keyOffAffectsPorta(song.dispatchChanOfChan[i])) {
         chan[i].portaNote=-1;
         chan[i].portaSpeed=-1;
         dispatchCmd(DivCommand(DIV_CMD_HINT_PORTA,i,CLAMP(chan[i].portaNote,-128,127),MAX(chan[i].portaSpeed,0)));
-        /*if (i==2 && song.sysOfChan[i]==DIV_SYSTEM_SMS) {
-          chan[i+1].portaNote=-1;
-          chan[i+1].portaSpeed=-1;
-        }*/
       }
       chan[i].scheduledSlideReset=true;
     }
@@ -839,7 +835,7 @@ void DivEngine::processRow(int i, bool afterDelay) {
     // ...unless there's a way to trigger keyOn twice
     if (!chan[i].keyOn) {
       // the behavior of arpeggio reset upon note off varies per system
-      if (disCont[song.dispatchOfChan[i]].dispatch->keyOffAffectsArp(song.dispatchChanOfChan[i])) {
+      if (song.dispatchChanOfChan[i]>=0) if (disCont[song.dispatchOfChan[i]].dispatch->keyOffAffectsArp(song.dispatchChanOfChan[i])) {
         chan[i].arp=0;
         dispatchCmd(DivCommand(DIV_CMD_HINT_ARPEGGIO,i,chan[i].arp));
       }
@@ -1039,7 +1035,7 @@ void DivEngine::processRow(int i, bool afterDelay) {
           // COMPAT FLAG: limit slide range
           // - this confines pitch slides from dispatch->getPortaFloor to C-8 (I think)
           // - yep, the lowest portamento note depends on the system...
-          chan[i].portaNote=song.limitSlides?disCont[song.dispatchOfChan[i]].dispatch->getPortaFloor(song.dispatchChanOfChan[i]):-60;
+          chan[i].portaNote=(song.limitSlides && song.dispatchChanOfChan[i]>=0)?disCont[song.dispatchOfChan[i]].dispatch->getPortaFloor(song.dispatchChanOfChan[i]):-60;
           chan[i].portaSpeed=effectVal;
           dispatchCmd(DivCommand(DIV_CMD_HINT_PORTA,i,CLAMP(chan[i].portaNote,-128,127),MAX(chan[i].portaSpeed,0)));
           chan[i].portaStop=true;
@@ -1684,7 +1680,7 @@ void DivEngine::processRow(int i, bool afterDelay) {
             chan[i].portaNote=song.limitSlides?0x60:255;
           } else {
             // COMPAT FLAG: limit slide range
-            chan[i].portaNote=song.limitSlides?disCont[song.dispatchOfChan[i]].dispatch->getPortaFloor(song.dispatchChanOfChan[i]):-60;
+            chan[i].portaNote=(song.limitSlides && song.dispatchChanOfChan[i]>=0)?disCont[song.dispatchOfChan[i]].dispatch->getPortaFloor(song.dispatchChanOfChan[i]):-60;
           }
           chan[i].portaSpeed=effectVal;
           chan[i].portaStop=true;
@@ -2080,7 +2076,10 @@ bool DivEngine::nextTick(bool noAccum, bool inhibitLowLat) {
       if (note.volume>=0 && !disCont[song.dispatchOfChan[note.channel]].dispatch->isVolGlobal()) {
         // map velocity to curve and then to equivalent chip volume
         float curvedVol=pow((float)note.volume/127.0f,midiVolExp);
-        int mappedVol=disCont[song.dispatchOfChan[note.channel]].dispatch->mapVelocity(song.dispatchChanOfChan[note.channel],curvedVol);
+        int mappedVol=0;
+        if (song.dispatchChanOfChan[note.channel]>=0) {
+          mappedVol=disCont[song.dispatchOfChan[note.channel]].dispatch->mapVelocity(song.dispatchChanOfChan[note.channel],curvedVol);
+        }
         // fire command
         dispatchCmd(DivCommand(DIV_CMD_VOLUME,note.channel,mappedVol));
       }
@@ -2094,7 +2093,10 @@ bool DivEngine::nextTick(bool noAccum, bool inhibitLowLat) {
       chan[note.channel].lastIns=note.ins;
     } else {
       // note off
-      DivMacroInt* macroInt=disCont[song.dispatchOfChan[note.channel]].dispatch->getChanMacroInt(song.dispatchChanOfChan[note.channel]);
+      DivMacroInt* macroInt=NULL;
+      if (song.dispatchChanOfChan[note.channel]>=0) {
+        macroInt=disCont[song.dispatchOfChan[note.channel]].dispatch->getChanMacroInt(song.dispatchChanOfChan[note.channel]);
+      }
       if (macroInt!=NULL) {
         // if the current instrument has a release point in any macros and
         // volume is per-channel, send a note release instead of a note off
@@ -2463,7 +2465,7 @@ bool DivEngine::nextTick(bool noAccum, bool inhibitLowLat) {
                   chan[i].stopOnOff=false;
                 }
                 // depending on the system, portamento may still be disabled
-                if (disCont[song.dispatchOfChan[i]].dispatch->keyOffAffectsPorta(song.dispatchChanOfChan[i])) {
+                if (song.dispatchChanOfChan[i]>=0) if (disCont[song.dispatchOfChan[i]].dispatch->keyOffAffectsPorta(song.dispatchChanOfChan[i])) {
                   chan[i].portaNote=-1;
                   chan[i].portaSpeed=-1;
                   dispatchCmd(DivCommand(DIV_CMD_HINT_PORTA,i,CLAMP(chan[i].portaNote,-128,127),MAX(chan[i].portaSpeed,0)));
@@ -2565,6 +2567,7 @@ bool DivEngine::nextTick(bool noAccum, bool inhibitLowLat) {
     shallStopSched=false;
     // reset all chan oscs
     for (int i=0; i<song.chans; i++) {
+      if (song.dispatchChanOfChan[i]<0) continue;
       DivDispatchOscBuffer* buf=disCont[song.dispatchOfChan[i]].dispatch->getOscBuffer(song.dispatchChanOfChan[i]);
       if (buf!=NULL) {
         buf->reset();
diff --git a/src/engine/song.cpp b/src/engine/song.cpp
index dad02d708..970dae4b6 100644
--- a/src/engine/song.cpp
+++ b/src/engine/song.cpp
@@ -710,17 +710,23 @@ void DivSong::recalcChans() {
   int chanIndex=0;
   memset(isInsTypePossible,0,DIV_INS_MAX*sizeof(bool));
   for (int i=0; i<systemLen; i++) {
+    const DivSysDef* sysDef=DivEngine::getSystemDef(system[i]);
     int chanCount=systemChans[i];
     int firstChan=chans;
     chans+=chanCount;
     for (int j=0; j<chanCount; j++) {
       sysOfChan[chanIndex]=system[i];
       dispatchOfChan[chanIndex]=i;
-      dispatchChanOfChan[chanIndex]=j;
+      if (sysDef==NULL) {
+        dispatchChanOfChan[chanIndex]=-1;
+      } else if (j<sysDef->maxChans) {
+        dispatchChanOfChan[chanIndex]=j;
+      } else {
+        dispatchChanOfChan[chanIndex]=-1;
+      }
       dispatchFirstChan[chanIndex]=firstChan;
       chanIndex++;
 
-      const DivSysDef* sysDef=DivEngine::getSystemDef(system[i]);
       if (sysDef!=NULL) {
         if (sysDef->chanInsType[j][0]!=DIV_INS_NULL) {
           isInsTypePossible[sysDef->chanInsType[j][0]]=true;
diff --git a/src/engine/sysDef.cpp b/src/engine/sysDef.cpp
index 24fd6246b..4d3f78e08 100644
--- a/src/engine/sysDef.cpp
+++ b/src/engine/sysDef.cpp
@@ -314,6 +314,7 @@ const char* DivEngine::getChannelName(int chan) {
   if (chan<0 || chan>song.chans) return "??";
   if (!curSubSong->chanName[chan].empty()) return curSubSong->chanName[chan].c_str();
   if (sysDefs[song.sysOfChan[chan]]==NULL) return "??";
+  if (song.dispatchChanOfChan[chan]<0) return "??";
   
   const char* ret=sysDefs[song.sysOfChan[chan]]->chanNames[song.dispatchChanOfChan[chan]];
   if (ret==NULL) return "??";
@@ -324,6 +325,7 @@ const char* DivEngine::getChannelShortName(int chan) {
   if (chan<0 || chan>song.chans) return "??";
   if (!curSubSong->chanShortName[chan].empty()) return curSubSong->chanShortName[chan].c_str();
   if (sysDefs[song.sysOfChan[chan]]==NULL) return "??";
+  if (song.dispatchChanOfChan[chan]<0) return "??";
   
   const char* ret=sysDefs[song.sysOfChan[chan]]->chanShortNames[song.dispatchChanOfChan[chan]];
   if (ret==NULL) return "??";
@@ -333,18 +335,21 @@ const char* DivEngine::getChannelShortName(int chan) {
 int DivEngine::getChannelType(int chan) {
   if (chan<0 || chan>song.chans) return DIV_CH_NOISE;
   if (sysDefs[song.sysOfChan[chan]]==NULL) return DIV_CH_NOISE;
+  if (song.dispatchChanOfChan[chan]<0) return DIV_CH_NOISE;
   return sysDefs[song.sysOfChan[chan]]->chanTypes[song.dispatchChanOfChan[chan]];
 }
 
 DivInstrumentType DivEngine::getPreferInsType(int chan) {
   if (chan<0 || chan>song.chans) return DIV_INS_STD;
   if (sysDefs[song.sysOfChan[chan]]==NULL) return DIV_INS_STD;
+  if (song.dispatchChanOfChan[chan]<0) return DIV_INS_STD;
   return sysDefs[song.sysOfChan[chan]]->chanInsType[song.dispatchChanOfChan[chan]][0];
 }
 
 DivInstrumentType DivEngine::getPreferInsSecondType(int chan) {
   if (chan<0 || chan>song.chans) return DIV_INS_NULL;
   if (sysDefs[song.sysOfChan[chan]]==NULL) return DIV_INS_NULL;
+  if (song.dispatchChanOfChan[chan]<0) return DIV_INS_NULL;
   return sysDefs[song.sysOfChan[chan]]->chanInsType[song.dispatchChanOfChan[chan]][1];
 }
 
diff --git a/src/engine/wavOps.cpp b/src/engine/wavOps.cpp
index d65af451d..dbe6f24fa 100644
--- a/src/engine/wavOps.cpp
+++ b/src/engine/wavOps.cpp
@@ -487,7 +487,7 @@ void DivEngine::runExportThread() {
           }
         }
         for (int j=0; j<song.chans; j++) {
-          if (disCont[song.dispatchOfChan[j]].dispatch!=NULL) {
+          if (disCont[song.dispatchOfChan[j]].dispatch!=NULL && song.dispatchChanOfChan[j]>=0) {
             disCont[song.dispatchOfChan[j]].dispatch->muteChannel(song.dispatchChanOfChan[j],isMuted[j]);
           }
         }
@@ -566,7 +566,7 @@ void DivEngine::runExportThread() {
 
       for (int i=0; i<song.chans; i++) {
         isMuted[i]=false;
-        if (disCont[song.dispatchOfChan[i]].dispatch!=NULL) {
+        if (disCont[song.dispatchOfChan[i]].dispatch!=NULL && song.dispatchChanOfChan[i]>=0) {
           disCont[song.dispatchOfChan[i]].dispatch->muteChannel(song.dispatchChanOfChan[i],false);
         }
       }
diff --git a/src/gui/debugWindow.cpp b/src/gui/debugWindow.cpp
index 96d0a2dce..81fae0061 100644
--- a/src/gui/debugWindow.cpp
+++ b/src/gui/debugWindow.cpp
@@ -121,6 +121,8 @@ void FurnaceGUI::drawDebug() {
         ImGui::TextColored(uiColors[GUI_COLOR_ACCENT_PRIMARY],"Ch. %d: %d, %d",i,e->song.dispatchOfChan[i],e->song.dispatchChanOfChan[i]);
         if (ch==NULL) {
           ImGui::Text("NULL");
+        } else if (e->song.dispatchChanOfChan[i]<0) {
+          ImGui::Text("---");
         } else {
           putDispatchChan(ch,e->song.dispatchChanOfChan[i],e->song.sysOfChan[i]);
         }