diff --git a/src/gui/gui.h b/src/gui/gui.h
index 53b2f1715..e2c61b9be 100644
--- a/src/gui/gui.h
+++ b/src/gui/gui.h
@@ -1019,7 +1019,7 @@ class FurnaceGUI {
   void drawSSGEnv(unsigned char type, const ImVec2& size);
   void drawWaveform(unsigned char type, bool opz, const ImVec2& size);
   void drawAlgorithm(unsigned char alg, FurnaceGUIFMAlgs algType, const ImVec2& size);
-  void drawFMEnv(unsigned char tl, unsigned char ar, unsigned char dr, unsigned char d2r, unsigned char rr, unsigned char sl, float maxTl, float maxArDr, const ImVec2& size);
+  void drawFMEnv(unsigned char tl, unsigned char ar, unsigned char dr, unsigned char d2r, unsigned char rr, unsigned char sl, unsigned char sus, unsigned char egt, unsigned char algOrGlobalSus, float maxTl, float maxArDr, const ImVec2& size, unsigned short instType);
   void drawSysConf(int i);
 
   // these ones offer ctrl-wheel fine value changes.
diff --git a/src/gui/insEdit.cpp b/src/gui/insEdit.cpp
index f53db474c..e9e69084f 100644
--- a/src/gui/insEdit.cpp
+++ b/src/gui/insEdit.cpp
@@ -901,7 +901,7 @@ void FurnaceGUI::drawAlgorithm(unsigned char alg, FurnaceGUIFMAlgs algType, cons
   }
 }
 
-void FurnaceGUI::drawFMEnv(unsigned char tl, unsigned char ar, unsigned char dr, unsigned char d2r, unsigned char rr, unsigned char sl, float maxTl, float maxArDr, const ImVec2& size) {
+void FurnaceGUI::drawFMEnv(unsigned char tl, unsigned char ar, unsigned char dr, unsigned char d2r, unsigned char rr, unsigned char sl, unsigned char sus, unsigned char egt, unsigned char algOrGlobalSus, float maxTl, float maxArDr, const ImVec2& size, unsigned short instType) {
   ImDrawList* dl=ImGui::GetWindowDrawList();
   ImGuiWindow* window=ImGui::GetCurrentWindow();
 
@@ -918,6 +918,10 @@ void FurnaceGUI::drawFMEnv(unsigned char tl, unsigned char ar, unsigned char dr,
   if (ImGui::ItemAdd(rect,ImGui::GetID("alg"))) {
     ImGui::RenderFrame(rect.Min,rect.Max,ImGui::GetColorU32(ImGuiCol_FrameBg),true,style.FrameRounding);
 
+    //Adjust for OPLL global sustain setting
+    if (instType==DIV_INS_OPLL && algOrGlobalSus==1.0){
+      rr = 5.0;
+    }
     //calculate x positions
     float arPos=float(maxArDr-ar)/maxArDr; //peak of AR, start of DR
     float drPos=arPos+((sl/15.0)*(float(maxArDr-dr)/maxArDr)); //end of DR, start of D2R
@@ -951,7 +955,7 @@ void FurnaceGUI::drawFMEnv(unsigned char tl, unsigned char ar, unsigned char dr,
       //addAALine(dl,pos3,posSLineVEnd,colorS); //draw vert. line through sustain level
       addAALine(dl,pos1,pos2,color); //A
       addAALine(dl,pos2,posDecayRate0Pt,color); //Line from A to end of graph
-    } else if (d2r==0.0) { //if D2R = 0, the envelope stays at the sustain level forever
+    } else if (d2r==0.0 || (instType==DIV_INS_OPL && sus==1.0) || (instType==DIV_INS_OPLL && egt!=0.0)) { //envelope stays at the sustain level forever
       dl->AddTriangleFilled(posRStart,posREnd,pos1,colorS); //draw release as shaded triangle behind everything
       addAALine(dl,pos3,posSLineHEnd,colorS); //draw horiz line through sustain level
       addAALine(dl,pos3,posSLineVEnd,colorS); //draw vert. line through sustain level
@@ -1808,7 +1812,7 @@ void FurnaceGUI::drawInsEdit() {
                     }
 
                     ImGui::TableNextColumn();
-                    drawFMEnv(op.tl&maxTl,op.ar&maxArDr,op.dr&maxArDr,(ins->type==DIV_INS_OPL || ins->type==DIV_INS_OPLL)?((op.rr&15)*2):op.d2r&31,op.rr&15,op.sl&15,maxTl,maxArDr,ImVec2(ImGui::GetContentRegionAvail().x,sliderHeight));
+                    drawFMEnv(op.tl&maxTl,op.ar&maxArDr,op.dr&maxArDr,(ins->type==DIV_INS_OPL || ins->type==DIV_INS_OPLL)?((op.rr&15)*2):op.d2r&31,op.rr&15,op.sl&15,op.sus,op.ssgEnv&8,ins->fm.alg,maxTl,maxArDr,ImVec2(ImGui::GetContentRegionAvail().x,sliderHeight),ins->type);
 
                     ImGui::PopID();
                   }
@@ -1891,7 +1895,7 @@ void FurnaceGUI::drawInsEdit() {
                     }
 
                     //52.0 controls vert scaling; default 96
-                    drawFMEnv(op.tl&maxTl,op.ar&maxArDr,op.dr&maxArDr,(ins->type==DIV_INS_OPL || ins->type==DIV_INS_OPLL)?((op.rr&15)*2):op.d2r&31,op.rr&15,op.sl&15,maxTl,maxArDr,ImVec2(ImGui::GetContentRegionAvail().x,52.0*dpiScale));
+                    drawFMEnv(op.tl&maxTl,op.ar&maxArDr,op.dr&maxArDr,(ins->type==DIV_INS_OPL || ins->type==DIV_INS_OPLL)?((op.rr&15)*2):op.d2r&31,op.rr&15,op.sl&15,op.sus,op.ssgEnv&8,ins->fm.alg,maxTl,maxArDr,ImVec2(ImGui::GetContentRegionAvail().x,52.0*dpiScale),ins->type);
                     //P(CWSliderScalar(FM_NAME(FM_AR),ImGuiDataType_U8,&op.ar,&_ZERO,&_THIRTY_ONE)); rightClickable
                     if (ImGui::BeginTable("opParams",2,ImGuiTableFlags_SizingStretchProp)) {
                       ImGui::TableSetupColumn("c0",ImGuiTableColumnFlags_WidthStretch,0.0); \