diff --git a/MicroDexed.ino b/MicroDexed.ino
index 4cd0f88..3caa5c3 100644
--- a/MicroDexed.ino
+++ b/MicroDexed.ino
@@ -175,7 +175,7 @@ AudioConnection * dynamicConnections[NUM_DEXED * 4];
 #endif
 void create_audio_engine_chain(uint8_t instance_id)
 {
-  MicroDexed[instance_id] = new AudioSourceMicroDexed(SAMPLE_RATE);
+  MicroDexed[instance_id] = new AudioSourceMicroDexed(SAMPLE_RATE, instance_id);
   mono2stereo[instance_id] = new AudioEffectMonoStereo();
 #if defined(USE_FX)
   chorus_modulator[instance_id] = new AudioSynthWaveform();
@@ -2458,6 +2458,7 @@ void SerialPrintFormatInt3(uint8_t num)
   Serial.print(buf);
 }
 
+#ifdef TEENSY3_6
 /* From: https://forum.pjrc.com/threads/33443-How-to-display-free-ram */
 extern "C" char* sbrk(int incr);
 uint32_t FreeMem(void)
@@ -2465,6 +2466,15 @@ uint32_t FreeMem(void)
   char top;
   return &top - reinterpret_cast<char*>(sbrk(0));
 }
+#else
+/* From: https://forum.pjrc.com/threads/33443-How-to-display-free-ram */
+extern unsigned long _heap_end;
+extern char *__brkval;
+int FreeMem(void)
+{
+  return (char *)&_heap_end - __brkval;
+}
+#endif
 /*
   uint32_t FreeMem(void) { // for Teensy 3.0
   uint32_t stackTop;
diff --git a/config.h b/config.h
index 078950e..1d9ac22 100644
--- a/config.h
+++ b/config.h
@@ -59,7 +59,7 @@
 // sed -i.orig 's/^#define USB_MIDI_SYSEX_MAX 290/#define USB_MIDI_SYSEX_MAX 4104/' /usr/local/arduino-teensy/hardware/teensy/avr/cores/teensy4/usb_midi.h
 //#define USB_MIDI_SYSEX_MAX 4104
 
-#define VERSION "1.0.17"
+#define VERSION "1.0.18"
 
 //*************************************************************************************************
 //* DEVICE SETTINGS
@@ -335,7 +335,7 @@
 
 #define TRANSPOSE_FIX 24
 //#define VOICE_SILENCE_LEVEL 1069
-#define VOICE_SILENCE_LEVEL 4000
+#define VOICE_SILENCE_LEVEL 1100
 
 // Audio
 #ifdef TGA_AUDIO_BOARD
diff --git a/controllers.h b/controllers.h
index ca7c002..32bc303 100644
--- a/controllers.h
+++ b/controllers.h
@@ -52,12 +52,12 @@ class FmMod {
 
     void setRange(uint8_t r)
     {
-      range = r < 0 && r > 99 ? 0 : r;
+      range = r < 0 || r > 99 ? 0 : r;
     }
 
     void setTarget(uint8_t assign)
     {
-      assign = assign < 0 && assign > 7 ? 0 : assign;
+      assign = assign < 0 || assign > 7 ? 0 : assign;
       pitch = assign & 1; // PITCH
       amp = assign & 2; // AMP
       eg = assign & 4; // EG
diff --git a/dexed.cpp b/dexed.cpp
index b7d888d..d077919 100644
--- a/dexed.cpp
+++ b/dexed.cpp
@@ -43,7 +43,7 @@
 
 extern config_t configuration;
 
-Dexed::Dexed(int rate)
+Dexed::Dexed(uint16_t rate, uint8_t instance_id)
 {
   uint8_t i;
 
@@ -89,6 +89,8 @@ Dexed::Dexed(int rate)
   sustain = false;
 
   setEngineType(DEXED_ENGINE);
+
+  id = instance_id;
 }
 
 Dexed::~Dexed()
@@ -265,6 +267,12 @@ void Dexed::keydown(int16_t pitch, uint8_t velo) {
         voices[note].dx7_note->oscSync();
       voices[i].key_pressed_timer = millis();
       keydown_counter++;
+#ifdef DEBUG
+      Serial.print(F("Start voice: "));
+      Serial.print(note, DEC);
+      Serial.print(F(" pitch: "));
+      Serial.println(pitch, DEC);
+#endif
       break;
     }
     else
@@ -309,13 +317,24 @@ void Dexed::keyup(int16_t pitch) {
     if ( voices[note].midi_note == pitch && voices[note].keydown ) {
       voices[note].keydown = false;
       voices[note].key_pressed_timer = 0;
-
+#ifdef DEBUG
+      Serial.print(F("Stop voice: "));
+      Serial.print(note, DEC);
+      Serial.print(F(" pitch: "));
+      Serial.println(pitch, DEC);
+      Serial.print(F(" id: "));
+      Serial.println(id, DEC);
+#endif
       break;
     }
   }
 
   // note not found ?
   if ( note >= max_notes ) {
+#ifdef DEBUG
+    Serial.print(F("Note not found: "));
+    Serial.println(pitch, DEC);
+#endif
     return;
   }
 
@@ -472,7 +491,8 @@ uint8_t Dexed::getNumNotesPlaying(void)
   uint8_t op_carrier = controllers.core->get_carrier_operators(data[134]); // look for carriers
   uint8_t i;
   uint8_t count_playing_voices = 0;
-
+  VoiceStatus voiceStatus;
+  
   for (i = 0; i < max_notes; i++)
   {
     if (voices[i].live == true)
@@ -483,13 +503,29 @@ uint8_t Dexed::getNumNotesPlaying(void)
       memset(&voiceStatus, 0, sizeof(VoiceStatus));
       voices[i].dx7_note->peekVoiceStatus(voiceStatus);
 
+#ifdef DEBUG
+      Serial.println(i);
+      Serial.print("ALG: ");
+      Serial.println(data[134]+1);
+#endif
+
       for (uint8_t op = 0; op < 6; op++)
       {
         if ((op_carrier & (1 << op)))
         {
           // this voice is a carrier!
           op_carrier_num++;
-          if (voiceStatus.amp[op] <= VOICE_SILENCE_LEVEL && voiceStatus.ampStep[op] == 4)
+
+#ifdef DEBUG
+          Serial.print("OP: ");
+          Serial.print(op);
+          Serial.print(" AMP_STEP: ");
+          Serial.print(voiceStatus.ampStep[op],DEC);
+          Serial.print(" AMP: ");
+          Serial.println(voiceStatus.amp[op],DEC);
+#endif
+
+          if (voiceStatus.amp[op] < VOICE_SILENCE_LEVEL && voiceStatus.ampStep[op] >= 3)
           {
             // this voice produces no audio output
             op_amp++;
@@ -497,6 +533,22 @@ uint8_t Dexed::getNumNotesPlaying(void)
         }
       }
 
+      /*
+            Serial.print(F("ID="));
+            Serial.print(id, DEC);
+            Serial.print(F(" OP carrier="));
+            Serial.print(op_carrier_num, DEC);
+            Serial.print(F(" OP amp="));
+            Serial.println(op_amp, DEC);
+      */
+
+#ifdef DEBUG
+          Serial.print("OP_AMP: ");
+          Serial.print(op_amp);
+          Serial.print(" OP_CARRIER_NUM: ");
+          Serial.println(op_carrier_num);
+#endif
+
       if (op_amp == op_carrier_num)
       {
         // all carrier-operators are silent -> disable the voice
diff --git a/dexed.h b/dexed.h
index 47cc9b1..176b470 100644
--- a/dexed.h
+++ b/dexed.h
@@ -141,7 +141,7 @@ enum DexedVoiceParameters {
 class Dexed
 {
   public:
-    Dexed(int rate);
+    Dexed(uint16_t rate, uint8_t id);
     ~Dexed();
     void activate(void);
     void deactivate(void);
@@ -202,6 +202,7 @@ class Dexed
   protected:
     //static const uint8_t MAX_ACTIVE_NOTES = MAX_NOTES;
     //uint8_t max_notes = MAX_ACTIVE_NOTES;
+    uint8_t id;
     uint8_t max_notes = 0;
     int16_t currentNote;
     bool sustain;
@@ -210,7 +211,7 @@ class Dexed
     bool refreshMode;
     bool refreshVoice;
     uint8_t engineType;
-    VoiceStatus voiceStatus;
+    //VoiceStatus voiceStatus;
     Lfo lfo;
     FmCore* engineMsfa;
     EngineMkI* engineMkI;
diff --git a/fm_core.cpp b/fm_core.cpp
index 03331cc..131f38a 100644
--- a/fm_core.cpp
+++ b/fm_core.cpp
@@ -76,31 +76,40 @@ uint8_t FmCore::get_carrier_operators(uint8_t algorithm)
 
   for (uint8_t i = 0; i < 6; i++)
   {
-    if ((alg.ops[i]&OUT_BUS_ADD) == OUT_BUS_ADD)
+    if ((alg.ops[i] & 7) == OUT_BUS_ADD)
       op_out |= 1 << i;
   }
 
   return op_out;
 }
 
-void FmCore::dump() {
-#ifdef VERBOSE
-  for (int i = 0; i < 32; i++) {
-    cout << (i + 1) << ":";
+void FmCore::dump(void)
+{
+#ifdef DEBUG
+  for (uint8_t i = 0; i < 32; i++)
+  {
+    Serial.print(i + 1);
+    Serial.print(":");
     const FmAlgorithm &alg = algorithms[i];
-    for (int j = 0; j < 6; j++) {
-      int flags = alg.ops[j];
-      cout << " ";
-      if (flags & FB_IN) cout << "[";
-      cout << (flags & IN_BUS_ONE ? "1" : flags & IN_BUS_TWO ? "2" : "0") << "->";
-      cout << (flags & OUT_BUS_ONE ? "1" : flags & OUT_BUS_TWO ? "2" : "0");
-      if (flags & OUT_BUS_ADD) cout << "+";
-      //cout << alg.ops[j].in << "->" << alg.ops[j].out;
-      if (flags & FB_OUT) cout << "]";
+    for (uint8_t j = 0; j < 6; j++)
+    {
+      uint8_t flags = alg.ops[j];
+      Serial.print(" ");
+      if (flags & FB_IN)
+        Serial.print("[");
+      Serial.print(flags & IN_BUS_ONE ? "1" : flags & IN_BUS_TWO ? "2" : "0");
+      Serial.print("->");
+      Serial.print(flags & OUT_BUS_ONE ? "1" : flags & OUT_BUS_TWO ? "2" : "0");
+      if (flags & OUT_BUS_ADD)
+        Serial.print("+");
+      if (flags & FB_OUT)
+        Serial.print("]");
     }
-    cout << " " << n_out(alg);
-    cout << endl;
+    Serial.print(" ");
+    Serial.println(n_out(alg));
   }
+#else
+  ;
 #endif
 }
 
diff --git a/source_microdexed.h b/source_microdexed.h
index e46e867..f324807 100644
--- a/source_microdexed.h
+++ b/source_microdexed.h
@@ -10,7 +10,7 @@ class AudioSourceMicroDexed : public AudioStream, public Dexed {
     uint32_t xrun = 0;
     uint16_t render_time_max = 0;
 
-    AudioSourceMicroDexed(int sample_rate) : AudioStream(0, NULL), Dexed(sample_rate) { };
+    AudioSourceMicroDexed(uint16_t sample_rate, uint8_t id) : AudioStream(0, NULL), Dexed(sample_rate,id) { };
 
     void update(void)
     {