diff --git a/src/gui/insEdit.cpp b/src/gui/insEdit.cpp
index a58feea87..dca41f17f 100644
--- a/src/gui/insEdit.cpp
+++ b/src/gui/insEdit.cpp
@@ -943,7 +943,7 @@ void FurnaceGUI::drawFMEnv(unsigned char tl, unsigned char ar, unsigned char dr,
   ImU32 colorR=ImGui::GetColorU32(uiColors[GUI_COLOR_FM_ENVELOPE_RELEASE]); // Relsease triangle
   ImU32 colorS=ImGui::GetColorU32(uiColors[GUI_COLOR_FM_ENVELOPE_SUS_GUIDE]); // Sustain horiz/vert line color
   ImGui::ItemSize(size,style.FramePadding.y);
-  if (ImGui::ItemAdd(rect,ImGui::GetID("alg"))) {
+  if (ImGui::ItemAdd(rect,ImGui::GetID("fmEnv"))) {
     ImGui::RenderFrame(rect.Min,rect.Max,ImGui::GetColorU32(ImGuiCol_FrameBg),true,style.FrameRounding);
 
     //Adjust for OPLL global sustain setting
@@ -1003,7 +1003,7 @@ void FurnaceGUI::drawFMEnv(unsigned char tl, unsigned char ar, unsigned char dr,
 }
 
 void FurnaceGUI::drawGBEnv(unsigned char vol, unsigned char len, unsigned char sLen, bool dir, const ImVec2& size) {
-  //ImDrawList* dl=ImGui::GetWindowDrawList();
+  ImDrawList* dl=ImGui::GetWindowDrawList();
   ImGuiWindow* window=ImGui::GetCurrentWindow();
 
   ImVec2 minArea=window->DC.CursorPos;
@@ -1013,13 +1013,50 @@ void FurnaceGUI::drawGBEnv(unsigned char vol, unsigned char len, unsigned char s
   );
   ImRect rect=ImRect(minArea,maxArea);
   ImGuiStyle& style=ImGui::GetStyle();
-  //ImU32 color=ImGui::GetColorU32(uiColors[GUI_COLOR_FM_ENVELOPE]);
+  ImU32 color=ImGui::GetColorU32(uiColors[GUI_COLOR_FM_ENVELOPE]);
   //ImU32 colorS=ImGui::GetColorU32(uiColors[GUI_COLOR_FM_ENVELOPE_SUS_GUIDE]); // Sustain horiz/vert line color
   ImGui::ItemSize(size,style.FramePadding.y);
-  if (ImGui::ItemAdd(rect,ImGui::GetID("alg"))) {
+  if (ImGui::ItemAdd(rect,ImGui::GetID("gbEnv"))) {
     ImGui::RenderFrame(rect.Min,rect.Max,ImGui::GetColorU32(ImGuiCol_FrameBg),true,style.FrameRounding);
+    
+    float volY=1.0-((float)vol/15.0);
+    float lenPos=(sLen>62)?1.0:((float)sLen/384.0);
+    float envEndPoint=((float)len/7.0)*((float)(dir?(15-vol):vol)/15.0);
 
-    // TODO: this whole thing
+    ImVec2 pos1=ImLerp(rect.Min,rect.Max,ImVec2(0.0,volY));
+    ImVec2 pos2;
+    if (dir) {
+      if (len>0) {
+        if (lenPos<envEndPoint) {
+          pos2=ImLerp(rect.Min,rect.Max,ImVec2(lenPos,volY*(1.0-(lenPos/envEndPoint))));
+        } else {
+          pos2=ImLerp(rect.Min,rect.Max,ImVec2(envEndPoint,0.0));
+        }
+      } else {
+        pos2=ImLerp(rect.Min,rect.Max,ImVec2(lenPos,volY));
+      }
+    } else {
+      if (len>0) {
+        if (lenPos<envEndPoint) {
+          pos2=ImLerp(rect.Min,rect.Max,ImVec2(lenPos,volY+(1.0-volY)*(lenPos/envEndPoint)));
+        } else {
+          pos2=ImLerp(rect.Min,rect.Max,ImVec2(envEndPoint,1.0));
+        }
+      } else {
+        pos2=ImLerp(rect.Min,rect.Max,ImVec2(lenPos,volY));
+      }
+    }
+    ImVec2 pos3=ImLerp(rect.Min,rect.Max,ImVec2(lenPos,(len>0 || sLen<63)?((dir && sLen>62)?0.0:1.0):volY));
+
+    addAALine(dl,pos1,pos2,color);
+    if (lenPos>=envEndPoint && sLen<63 && dir) {
+      pos3=ImLerp(rect.Min,rect.Max,ImVec2(lenPos,0.0));
+      addAALine(dl,pos2,pos3,color);
+      ImVec2 pos4=ImLerp(rect.Min,rect.Max,ImVec2(lenPos,1.0));
+      addAALine(dl,pos3,pos4,color);
+    } else {
+      addAALine(dl,pos2,pos3,color);
+    }
   }
 }