diff --git a/src/engine/engine.cpp b/src/engine/engine.cpp
index 14db7185..f685254a 100644
--- a/src/engine/engine.cpp
+++ b/src/engine/engine.cpp
@@ -176,6 +176,10 @@ bool DivEngine::isFMSystem(DivSystem sys) {
           sys==DIV_SYSTEM_YMU759);
 }
 
+bool DivEngine::isSTDSystem(DivSystem sys) {
+  return (sys!=DIV_SYSTEM_ARCADE && sys!=DIV_SYSTEM_YMU759);
+}
+
 const char* chanNames[11][17]={
   {"Channel 1", "Channel 2", "Channel 3", "Channel 4", "Channel 5", "Channel 6", "Channel 7", "Channel 8", "Channel 9", "Channel 10", "Channel 11", "Channel 12", "Channel 13", "Channel 14", "Channel 15", "Channel 16", "PCM"}, // YMU759
   {"FM 1", "FM 2", "FM 3", "FM 4", "FM 5", "FM 6", "Square 1", "Square 2", "Square 3", "Noise"}, // Genesis
@@ -1176,6 +1180,28 @@ void DivEngine::renderSamples() {
   }
 }
 
+void DivEngine::changeSystem(DivSystem which) {
+  quitDispatch();
+  isBusy.lock();
+  song.system=which;
+  chans=getChannelCount(song.system);
+  // instrument safety check
+  for (DivInstrument* i: song.ins) {
+    if (!isFMSystem(song.system) && i->mode) {
+      i->mode=false;
+    }
+    if (!isSTDSystem(song.system) && !i->mode) {
+      i->mode=true;
+    }
+  }
+  isBusy.unlock();
+  initDispatch();
+  isBusy.lock();
+  renderSamples();
+  reset();
+  isBusy.unlock();
+}
+
 DivInstrument* DivEngine::getIns(int index) {
   if (index<0 || index>=song.insLen) return &song.nullIns;
   return song.ins[index];
@@ -1244,6 +1270,7 @@ int DivEngine::addInstrument() {
   DivInstrument* ins=new DivInstrument;
   int insCount=(int)song.ins.size();
   ins->name=fmt::sprintf("Instrument %d",insCount);
+  ins->mode=isFMSystem(song.system);
   song.ins.push_back(ins);
   song.insLen=insCount+1;
   isBusy.unlock();
diff --git a/src/engine/engine.h b/src/engine/engine.h
index 5c4c13ee..1536f5cf 100644
--- a/src/engine/engine.h
+++ b/src/engine/engine.h
@@ -129,6 +129,9 @@ class DivEngine {
     // is FM system
     bool isFMSystem(DivSystem sys);
 
+    // is STD system
+    bool isSTDSystem(DivSystem sys);
+
     // get channel name
     const char* getChannelName(int chan);
 
@@ -195,6 +198,9 @@ class DivEngine {
     // public render samples
     void renderSamplesP();
 
+    // change system
+    void changeSystem(DivSystem which);
+
     // init dispatch
     void initDispatch();
 
diff --git a/src/engine/instrument.h b/src/engine/instrument.h
index 2d66898d..93ccce40 100644
--- a/src/engine/instrument.h
+++ b/src/engine/instrument.h
@@ -72,10 +72,10 @@ struct DivInstrumentSTD {
 struct DivInstrumentGB {
   unsigned char envVol, envDir, envLen, soundLen;
   DivInstrumentGB():
-    envVol(0),
+    envVol(15),
     envDir(0),
-    envLen(0),
-    soundLen(0) {}
+    envLen(2),
+    soundLen(64) {}
 };
 
 struct DivInstrumentC64 {
diff --git a/src/gui/gui.cpp b/src/gui/gui.cpp
index 4f78b40d..9ea69d5f 100644
--- a/src/gui/gui.cpp
+++ b/src/gui/gui.cpp
@@ -315,7 +315,7 @@ void FurnaceGUI::drawInsEdit() {
     } else {
       DivInstrument* ins=e->song.ins[curIns];
       ImGui::InputText("Name",&ins->name);
-      if (e->isFMSystem(e->song.system)) ImGui::Checkbox("FM",&ins->mode);
+      if (e->isFMSystem(e->song.system) && e->isSTDSystem(e->song.system)) ImGui::Checkbox("FM",&ins->mode);
 
       if (ins->mode) { // FM
         ImGui::SliderScalar("Algorithm",ImGuiDataType_U8,&ins->fm.alg,&_ZERO,&_SEVEN);
@@ -1280,6 +1280,12 @@ int FurnaceGUI::load(String path) {
   return 0;
 }
 
+#define sysChangeOption(x) \
+  if (ImGui::MenuItem(e->getSystemName(x),NULL,e->song.system==x)) { \
+    e->changeSystem(x); \
+    updateWindowTitle(); \
+  }
+
 bool FurnaceGUI::loop() {
   while (!quit) {
     SDL_Event ev;
@@ -1356,7 +1362,20 @@ bool FurnaceGUI::loop() {
         openFileDialog(GUI_FILE_SAVE);
       }
       ImGui::Separator();
-      ImGui::MenuItem("change platform...");
+      if (ImGui::BeginMenu("change platform...")) {
+        sysChangeOption(DIV_SYSTEM_GENESIS);
+        sysChangeOption(DIV_SYSTEM_GENESIS_EXT);
+        sysChangeOption(DIV_SYSTEM_SMS);
+        sysChangeOption(DIV_SYSTEM_GB);
+        sysChangeOption(DIV_SYSTEM_PCE);
+        sysChangeOption(DIV_SYSTEM_NES);
+        sysChangeOption(DIV_SYSTEM_C64_8580);
+        sysChangeOption(DIV_SYSTEM_C64_6581);
+        sysChangeOption(DIV_SYSTEM_ARCADE);
+        sysChangeOption(DIV_SYSTEM_YM2610);
+        sysChangeOption(DIV_SYSTEM_YM2610_EXT);
+        ImGui::EndMenu();
+      }
       ImGui::Separator();
       if (ImGui::MenuItem("exit")) {
         quit=true;