diff --git a/src/gui/gui.cpp b/src/gui/gui.cpp
index 6ad37fff4..55569a620 100644
--- a/src/gui/gui.cpp
+++ b/src/gui/gui.cpp
@@ -5235,9 +5235,15 @@ FurnaceGUI::FurnaceGUI():
 
   memset(waveGenAmp,0,sizeof(float)*16);
   memset(waveGenPhase,0,sizeof(float)*16);
-  memset(waveGenTL,0,sizeof(float)*4);
-  memset(waveGenMult,0,sizeof(int)*4);
-  memset(waveGenFB,0,sizeof(float)*4);
+  waveGenTL[0]=0.0f;
+  waveGenTL[1]=0.0f;
+  waveGenTL[2]=0.0f;
+  waveGenTL[3]=1.0f;
+  waveGenMult[0]=1;
+  waveGenMult[1]=1;
+  waveGenMult[2]=1;
+  waveGenMult[3]=1;
+  memset(waveGenFB,0,sizeof(int)*4);
   memset(waveGenFMCon1,0,sizeof(bool)*4);
   memset(waveGenFMCon2,0,sizeof(bool)*3);
   memset(waveGenFMCon3,0,sizeof(bool)*2);
diff --git a/src/gui/gui.h b/src/gui/gui.h
index 797f9fd71..7a67ac374 100644
--- a/src/gui/gui.h
+++ b/src/gui/gui.h
@@ -1566,7 +1566,7 @@ class FurnaceGUI {
   float waveGenPhase[16];
   float waveGenTL[4];
   int waveGenMult[4];
-  float waveGenFB[4];
+  int waveGenFB[4];
   bool waveGenFMCon1[4];
   bool waveGenFMCon2[3];
   bool waveGenFMCon3[2];
diff --git a/src/gui/waveEdit.cpp b/src/gui/waveEdit.cpp
index 9842d808b..80f3a3419 100644
--- a/src/gui/waveEdit.cpp
+++ b/src/gui/waveEdit.cpp
@@ -61,12 +61,31 @@ void FurnaceGUI::doGenerateWave() {
   if (wave->len<2) return;
 
   if (waveGenFM) {
+    float s0fb0=0;
+    float s0fb1=0;
+    float s1fb0=0;
+    float s1fb1=0;
+    float s2fb0=0;
+    float s2fb1=0;
+    float s3fb0=0;
+    float s3fb1=0;
     for (int i=0; i<wave->len; i++) {
       float pos=(float)i/(float)wave->len;
-      float s0=sin(pos*multFactors[waveGenMult[0]])*waveGenTL[0];
-      float s1=sin((pos+(waveGenFMCon1[0]?s0:0.0f))*multFactors[waveGenMult[1]])*waveGenTL[1];
-      float s2=sin((pos+(waveGenFMCon1[1]?s0:0.0f)+(waveGenFMCon2[0]?s1:0.0f))*multFactors[waveGenMult[2]])*waveGenTL[2];
-      float s3=sin((pos+(waveGenFMCon1[2]?s0:0.0f)+(waveGenFMCon2[1]?s1:0.0f)+(waveGenFMCon3[0]?s2:0.0f))*multFactors[waveGenMult[3]])*waveGenTL[3];
+      float s0=sin((pos+(waveGenFB[0]?((s0fb0+s0fb1)*pow(2.0f,waveGenFB[0]-8)):0.0f))*multFactors[waveGenMult[0]])*waveGenTL[0];
+      s0fb0=s0fb1;
+      s0fb1=s0;
+      
+      float s1=sin((pos+(waveGenFB[1]?((s1fb0+s1fb1)*pow(2.0f,waveGenFB[1]-8)):0.0f)+(waveGenFMCon1[0]?s0:0.0f))*multFactors[waveGenMult[1]])*waveGenTL[1];
+      s1fb0=s1fb1;
+      s1fb1=s1;
+
+      float s2=sin((pos+(waveGenFB[2]?((s2fb0+s2fb1)*pow(2.0f,waveGenFB[2]-8)):0.0f)+(waveGenFMCon1[1]?s0:0.0f)+(waveGenFMCon2[0]?s1:0.0f))*multFactors[waveGenMult[2]])*waveGenTL[2];
+      s2fb0=s2fb1;
+      s2fb1=s2;
+
+      float s3=sin((pos+(waveGenFB[3]?((s3fb0+s3fb1)*pow(2.0f,waveGenFB[3]-8)):0.0f)+(waveGenFMCon1[2]?s0:0.0f)+(waveGenFMCon2[1]?s1:0.0f)+(waveGenFMCon3[0]?s2:0.0f))*multFactors[waveGenMult[3]])*waveGenTL[3];
+      s3fb0=s3fb1;
+      s3fb1=s3;
 
       if (waveGenFMCon1[3]) finalResult[i]+=s0;
       if (waveGenFMCon2[2]) finalResult[i]+=s1;
@@ -394,7 +413,7 @@ void FurnaceGUI::drawWaveEdit() {
                   ImGui::TableNextColumn();
                   ImGui::SetNextItemWidth(ImGui::GetContentRegionAvail().x);
                   ImGui::PushID(i);
-                  if (CWSliderFloat("##WGFB",&waveGenFB[i],0.0f,7.0f)) {
+                  if (CWSliderInt("##WGFB",&waveGenFB[i],0,7)) {
                     doGenerateWave();
                   }
                   ImGui::PopID();