diff --git a/src/engine/platform/n163.cpp b/src/engine/platform/n163.cpp
index 7c9188d49..b7234a4ba 100644
--- a/src/engine/platform/n163.cpp
+++ b/src/engine/platform/n163.cpp
@@ -171,29 +171,43 @@ void DivPlatformN163::acquire(short* bufL, short* bufR, size_t start, size_t len
   }
 }
 
-void DivPlatformN163::updateWave(int wave, int pos, int len) {
+void DivPlatformN163::updateWave(int ch, int wave, int pos, int len) {
   len&=0xfc; // 4 nibble boundary
-  DivWavetable* wt=parent->getWave(wave);
-  for (int i=0; i<len; i++) {
-    unsigned char addr=(pos+i); // address (nibble each)
-    if (addr>=((0x78-(chanMax<<3))<<1)) { // avoid conflict with channel register area
-      break;
-    }
-    unsigned char mask=(addr&1)?0xf0:0x0f;
-    if (wt->max<1 || wt->len<1) {
-      rWriteMask(addr>>1,0,mask);
-    } else {
-      int data=wt->data[i*wt->len/len]*15/wt->max;
-      if (data<0) data=0;
-      if (data>15) data=15;
+  if (wave<0) {
+    // load from wave synth
+    for (int i=0; i<len; i++) {
+      unsigned char addr=(pos+i); // address (nibble each)
+      if (addr>=((0x78-(chanMax<<3))<<1)) { // avoid conflict with channel register area
+        break;
+      }
+      unsigned char mask=(addr&1)?0xf0:0x0f;
+      int data=chan[ch].ws.output[i];
       rWriteMask(addr>>1,(addr&1)?(data<<4):(data&0xf),mask);
     }
+  } else {
+    // load from custom
+    DivWavetable* wt=parent->getWave(wave);
+    for (int i=0; i<len; i++) {
+      unsigned char addr=(pos+i); // address (nibble each)
+      if (addr>=((0x78-(chanMax<<3))<<1)) { // avoid conflict with channel register area
+        break;
+      }
+      unsigned char mask=(addr&1)?0xf0:0x0f;
+      if (wt->max<1 || wt->len<1) {
+        rWriteMask(addr>>1,0,mask);
+      } else {
+        int data=wt->data[i*wt->len/len]*15/wt->max;
+        if (data<0) data=0;
+        if (data>15) data=15;
+        rWriteMask(addr>>1,(addr&1)?(data<<4):(data&0xf),mask);
+      }
+    }
   }
 }
 
 void DivPlatformN163::updateWaveCh(int ch) {
   if (ch<=chanMax) {
-    updateWave(chan[ch].wave,chan[ch].wavePos,chan[ch].waveLen);
+    updateWave(ch,-1,chan[ch].wavePos,chan[ch].waveLen);
     if (chan[ch].active && !isMuted[ch]) {
       chan[ch].volumeChanged=true;
     }
@@ -241,6 +255,7 @@ void DivPlatformN163::tick() {
     if (chan[i].std.wave.had) {
       if (chan[i].wave!=chan[i].std.wave.val) {
         chan[i].wave=chan[i].std.wave.val;
+        chan[i].ws.changeWave1(chan[i].wave);
         if (chan[i].waveMode&0x2) {
           chan[i].waveUpdated=true;
         }
@@ -249,6 +264,7 @@ void DivPlatformN163::tick() {
     if (chan[i].std.ex1.had) {
       if (chan[i].waveLen!=(chan[i].std.ex1.val&0xfc)) {
         chan[i].waveLen=chan[i].std.ex1.val&0xfc;
+        chan[i].ws.setWidth(chan[i].waveLen);
         if (chan[i].waveMode&0x2) {
           chan[i].waveUpdated=true;
         }
@@ -275,7 +291,7 @@ void DivPlatformN163::tick() {
       if (chan[i].loadWave!=chan[i].std.ex3.val) {
         chan[i].loadWave=chan[i].std.ex3.val;
         if (chan[i].loadMode&0x2) {
-          updateWave(chan[i].loadWave,chan[i].loadPos,chan[i].loadLen&0xfc);
+          updateWave(i,chan[i].loadWave,chan[i].loadPos,chan[i].loadLen&0xfc);
         }
       }
     }
@@ -296,7 +312,7 @@ void DivPlatformN163::tick() {
       if ((chan[i].loadMode&0x1)!=(chan[i].std.fms.val&0x1)) { // load now
         chan[i].loadMode=(chan[i].loadMode&~0x1)|(chan[i].std.fms.val&0x1);
         if (chan[i].loadMode&0x1) { // rising edge
-          updateWave(chan[i].loadWave,chan[i].loadPos,chan[i].loadLen&0xfc);
+          updateWave(i,chan[i].loadWave,chan[i].loadPos,chan[i].loadLen&0xfc);
         }
       }
     }
@@ -315,6 +331,11 @@ void DivPlatformN163::tick() {
       }
       chan[i].waveChanged=false;
     }
+    if (chan[i].active) {
+      if (chan[i].ws.tick()) {
+        chan[i].waveUpdated=true;
+      }
+    }
     if (chan[i].waveUpdated) {
       updateWaveCh(i);
       if (chan[i].active) {
@@ -353,11 +374,12 @@ int DivPlatformN163::dispatch(DivCommand c) {
       DivInstrument* ins=parent->getIns(chan[c.chan].ins);
       if (chan[c.chan].insChanged) {
         chan[c.chan].wave=ins->n163.wave;
+        chan[c.chan].ws.changeWave1(chan[c.chan].wave);
         chan[c.chan].wavePos=ins->n163.wavePos;
         chan[c.chan].waveLen=ins->n163.waveLen;
         chan[c.chan].waveMode=ins->n163.waveMode;
         chan[c.chan].waveChanged=true;
-        if (chan[c.chan].waveMode&0x3) {
+        if (chan[c.chan].waveMode&0x3 || ins->ws.enabled) {
           chan[c.chan].waveUpdated=true;
         }
         chan[c.chan].insChanged=false;
@@ -374,6 +396,7 @@ int DivPlatformN163::dispatch(DivCommand c) {
         chan[c.chan].volumeChanged=true;
       }
       chan[c.chan].std.init(ins);
+      chan[c.chan].ws.init(ins,chan[c.chan].waveLen,15,chan[c.chan].insChanged);
       break;
     }
     case DIV_CMD_NOTE_OFF:
@@ -472,7 +495,7 @@ int DivPlatformN163::dispatch(DivCommand c) {
     case DIV_CMD_N163_WAVE_LOAD:
       chan[c.chan].loadWave=c.value;
       if (chan[c.chan].loadMode&0x2) { // load when every waveform changes
-        updateWave(chan[c.chan].loadWave,chan[c.chan].loadPos,chan[c.chan].loadLen);
+        updateWave(c.chan,chan[c.chan].loadWave,chan[c.chan].loadPos,chan[c.chan].loadLen);
       }
       break;
     case DIV_CMD_N163_WAVE_LOADPOS:
@@ -484,13 +507,13 @@ int DivPlatformN163::dispatch(DivCommand c) {
     case DIV_CMD_N163_WAVE_LOADMODE:
       chan[c.chan].loadMode=c.value&0x3;
       if (chan[c.chan].loadMode&0x1) { // load now
-        updateWave(chan[c.chan].loadWave,chan[c.chan].loadPos,chan[c.chan].loadLen);
+        updateWave(c.chan,chan[c.chan].loadWave,chan[c.chan].loadPos,chan[c.chan].loadLen);
       }
       break;
     case DIV_CMD_N163_GLOBAL_WAVE_LOAD:
       loadWave=c.value;
       if (loadMode&0x2) { // load when every waveform changes
-        updateWave(loadWave,loadPos,loadLen);
+        updateWave(c.chan,loadWave,loadPos,loadLen);
       }
       break;
     case DIV_CMD_N163_GLOBAL_WAVE_LOADPOS:
@@ -502,7 +525,7 @@ int DivPlatformN163::dispatch(DivCommand c) {
     case DIV_CMD_N163_GLOBAL_WAVE_LOADMODE:
       loadMode=c.value&0x3;
       if (loadMode&0x3) { // load now
-        updateWave(loadWave,loadPos,loadLen);
+        updateWave(c.chan,loadWave,loadPos,loadLen);
       }
       break;
     case DIV_CMD_N163_CHANNEL_LIMIT:
@@ -562,6 +585,7 @@ void DivPlatformN163::notifyWaveChange(int wave) {
   for (int i=0; i<8; i++) {
     if (chan[i].wave==wave) {
       if (chan[i].waveMode&0x2) {
+        chan[i].ws.changeWave1(wave);
         chan[i].waveUpdated=true;
       }
     }
@@ -601,6 +625,8 @@ void DivPlatformN163::reset() {
   while (!writes.empty()) writes.pop();
   for (int i=0; i<8; i++) {
     chan[i]=DivPlatformN163::Channel();
+    chan[i].ws.setEngine(parent);
+    chan[i].ws.init(NULL,32,15,false);
   }
 
   n163.reset();
diff --git a/src/engine/platform/n163.h b/src/engine/platform/n163.h
index 70f842adf..2f68d6c9d 100644
--- a/src/engine/platform/n163.h
+++ b/src/engine/platform/n163.h
@@ -23,6 +23,7 @@
 #include "../dispatch.h"
 #include <queue>
 #include "../macroInt.h"
+#include "../waveSynth.h"
 #include "sound/n163/n163.hpp"
 
 class DivPlatformN163: public DivDispatch {
@@ -35,6 +36,7 @@ class DivPlatformN163: public DivDispatch {
     bool active, insChanged, freqChanged, volumeChanged, waveChanged, waveUpdated, keyOn, keyOff, inPorta;
     signed char vol, outVol, resVol;
     DivMacroInt std;
+    DivWaveSynth ws;
     Channel():
       freq(0),
       baseFreq(0),
@@ -79,7 +81,7 @@ class DivPlatformN163: public DivDispatch {
 
   n163_core n163;
   unsigned char regPool[128];
-  void updateWave(int wave, int pos, int len);
+  void updateWave(int ch, int wave, int pos, int len);
   void updateWaveCh(int ch);
   friend void putDispatchChan(void*,int,int);
 
diff --git a/src/engine/waveSynth.cpp b/src/engine/waveSynth.cpp
index e38ee228e..ce93105d4 100644
--- a/src/engine/waveSynth.cpp
+++ b/src/engine/waveSynth.cpp
@@ -18,6 +18,7 @@ bool DivWaveSynth::tick() {
   bool updated=first;
   first=false;
   if (!state.enabled) return updated;
+  if (width<1) return false;
 
   if (--divCounter<=0) {
     // run effect
@@ -84,8 +85,15 @@ bool DivWaveSynth::tick() {
   return updated;
 }
 
+void DivWaveSynth::setWidth(int val) {
+  width=val;
+  if (width<0) width=0;
+  if (width>256) width=256;
+}
+
 void DivWaveSynth::changeWave1(int num) {
   DivWavetable* w1=e->getWave(num);
+  if (width<1) return;
   for (int i=0; i<width; i++) {
     if (w1->max<1 || w1->len<1) {
       wave1[i]=0;
@@ -103,6 +111,7 @@ void DivWaveSynth::changeWave1(int num) {
 
 void DivWaveSynth::changeWave2(int num) {
   DivWavetable* w2=e->getWave(num);
+  if (width<1) return;
   for (int i=0; i<width; i++) {
     if (w2->max<1 || w2->len<1) {
       wave2[i]=0;
diff --git a/src/engine/waveSynth.h b/src/engine/waveSynth.h
index ccd8b23de..ecd6f8a86 100644
--- a/src/engine/waveSynth.h
+++ b/src/engine/waveSynth.h
@@ -47,6 +47,11 @@ class DivWaveSynth {
      * @return whether the wave has changed.
      */
     bool tick();
+    /**
+     * set the wave width.
+     * @param value the width.
+     */
+    void setWidth(int val);
     /**
      * change the first wave.
      * @param num wavetable number.
diff --git a/src/gui/guiConst.cpp b/src/gui/guiConst.cpp
index 1b292638c..bc5345aa5 100644
--- a/src/gui/guiConst.cpp
+++ b/src/gui/guiConst.cpp
@@ -385,8 +385,8 @@ const FurnaceGUIColorDef guiColors[GUI_COLOR_MAX]={
   D(GUI_COLOR_OSC_BORDER,"",ImVec4(0.4f,0.6f,0.95f,1.0f)),
   D(GUI_COLOR_OSC_WAVE,"",ImVec4(0.95f,0.95f,1.0f,1.0f)),
   D(GUI_COLOR_OSC_WAVE_PEAK,"",ImVec4(0.95f,0.95f,1.0f,1.0f)),
-  D(GUI_COLOR_OSC_REF,"",ImVec4(0.3f,0.3f,0.3f,1.0f)),
-  D(GUI_COLOR_OSC_GUIDE,"",ImVec4(0.3,0.3f,0.3f,1.0f)),
+  D(GUI_COLOR_OSC_REF,"",ImVec4(0.3,0.65f,1.0f,0.15f)),
+  D(GUI_COLOR_OSC_GUIDE,"",ImVec4(0.3,0.65f,1.0f,0.13f)),
 
   D(GUI_COLOR_VOLMETER_LOW,"",ImVec4(0.2f,0.6f,0.2f,1.0f)),
   D(GUI_COLOR_VOLMETER_HIGH,"",ImVec4(1.0f,0.9f,0.2f,1.0f)),
diff --git a/src/gui/osc.cpp b/src/gui/osc.cpp
index e43dee1e0..c7089a991 100644
--- a/src/gui/osc.cpp
+++ b/src/gui/osc.cpp
@@ -69,9 +69,6 @@ void FurnaceGUI::readOsc() {
   e->oscReadPos=readPos;
 }
 
-// TODO:
-// - draw reference level
-// - draw guidelines
 void FurnaceGUI::drawOsc() {
   if (nextWindow==GUI_WINDOW_OSCILLOSCOPE) {
     oscOpen=true;
@@ -115,6 +112,7 @@ void FurnaceGUI::drawOsc() {
     ImU32 color=ImGui::GetColorU32(isClipping?uiColors[GUI_COLOR_OSC_WAVE_PEAK]:uiColors[GUI_COLOR_OSC_WAVE]);
     ImU32 borderColor=ImGui::GetColorU32(uiColors[GUI_COLOR_OSC_BORDER]);
     ImU32 refColor=ImGui::GetColorU32(uiColors[GUI_COLOR_OSC_REF]);
+    ImU32 guideColor=ImGui::GetColorU32(uiColors[GUI_COLOR_OSC_GUIDE]);
     ImGui::ItemSize(size,style.FramePadding.y);
     if (ImGui::ItemAdd(rect,ImGui::GetID("wsDisplay"))) {
       // https://github.com/ocornut/imgui/issues/3710
@@ -162,11 +160,60 @@ void FurnaceGUI::drawOsc() {
 
       dl->AddLine(
         ImLerp(rect.Min,rect.Max,ImVec2(0.0f,0.5f)),
-        ImLerp(rect.Min,rect.Max,ImVec2(0.0f,0.5f)),
+        ImLerp(rect.Min,rect.Max,ImVec2(1.0f,0.5f)),
         refColor,
         dpiScale
       );
 
+      dl->AddLine(
+        ImLerp(rect.Min,rect.Max,ImVec2(0.48f,0.125f)),
+        ImLerp(rect.Min,rect.Max,ImVec2(0.52f,0.125f)),
+        guideColor,
+        dpiScale
+      );
+
+      dl->AddLine(
+        ImLerp(rect.Min,rect.Max,ImVec2(0.47f,0.25f)),
+        ImLerp(rect.Min,rect.Max,ImVec2(0.53f,0.25f)),
+        guideColor,
+        dpiScale
+      );
+
+      dl->AddLine(
+        ImLerp(rect.Min,rect.Max,ImVec2(0.45f,0.375f)),
+        ImLerp(rect.Min,rect.Max,ImVec2(0.55f,0.375f)),
+        guideColor,
+        dpiScale
+      );
+
+      dl->AddLine(
+        ImLerp(rect.Min,rect.Max,ImVec2(0.45f,0.625f)),
+        ImLerp(rect.Min,rect.Max,ImVec2(0.55f,0.625f)),
+        guideColor,
+        dpiScale
+      );
+
+      dl->AddLine(
+        ImLerp(rect.Min,rect.Max,ImVec2(0.47f,0.75f)),
+        ImLerp(rect.Min,rect.Max,ImVec2(0.53f,0.75f)),
+        guideColor,
+        dpiScale
+      );
+
+      dl->AddLine(
+        ImLerp(rect.Min,rect.Max,ImVec2(0.48f,0.875f)),
+        ImLerp(rect.Min,rect.Max,ImVec2(0.52f,0.875f)),
+        guideColor,
+        dpiScale
+      );
+
+      dl->AddLine(
+        ImLerp(rect.Min,rect.Max,ImVec2(0.5f,0.08f)),
+        ImLerp(rect.Min,rect.Max,ImVec2(0.5f,0.92f)),
+        guideColor,
+        dpiScale
+      );
+
       for (size_t i=0; i<512; i++) {
         float x=(float)i/512.0f;
         float y=oscValues[i]*oscZoom;