FIxed the generator function. You have to use all available optimizations

(especially LTO) at compilation for getting high performance.

MicroMDAPiano.ino

@@ -215,7 +215,7 @@ void loop()
     }
 
     elapsedMicros t1;
-    ep->process(audio_buffer_l, audio_buffer_r, AUDIO_BLOCK_SAMPLES);
+    ep->process(audio_buffer_l, audio_buffer_r);
     uint32_t t2 = t1;
     if (t2 > audio_block_time_ms) // everything greater 2.9ms is a buffer underrun!
       xrun++;
@@ -231,6 +231,7 @@ void loop()
       if (peak_l.read() > 0.99)
         peak++;
     }
+
 #ifndef TEENSY_AUDIO_BOARD
     for (uint8_t i = 0; i < AUDIO_BLOCK_SAMPLES; i++)
     {

mdaEPiano.cpp

@@ -332,14 +332,14 @@ float mdaEPiano::getParameter(int32_t index)     {
   }
 */
 
-void mdaEPiano::process(int16_t *outputs_r, int16_t *outputs_l, int32_t sampleFrames)
+void mdaEPiano::process(int16_t *outputs_r, int16_t *outputs_l)
 {
   int16_t v;
   float x, l, r, od = overdrive;
   int32_t i;
   int16_t frame;
 
-  for (frame = 0; frame < sampleFrames; frame++)
+  for (frame = 0; frame < AUDIO_BLOCK_SAMPLES; frame++)
   {
     VOICE *V = voice;
     l = r = 0.0f;
@@ -348,25 +348,21 @@ void mdaEPiano::process(int16_t *outputs_r, int16_t *outputs_l, int32_t sampleFr
       V->frac += V->delta;  //integer-based linear interpolation
       V->pos += V->frac >> 16;
       V->frac &= 0xFFFF;
-      if (V->pos > V->end) V->pos -= V->loop;
-      //i = waves[V->pos];
-      //i = (i << 7) + (V->frac >> 9) * (waves[V->pos + 1] - i) + 0x40400000;  //not working on intel mac !?!
-      //x = V->env * (*(float *)&i - 3.0f);  //fast int->float
-      //x = V->env * (float)i / 32768.0f;
+      if (V->pos > V->end)
+        V->pos -= V->loop;
       i = waves[V->pos] + ((V->frac * (waves[V->pos + 1] - waves[V->pos])) >> 16);
-      //x = V->env * (float)i / 32768.0f;
-
+      x = V->env * static_cast<float>(i) / 32768.0f;
       V->env = V->env * V->dec;  //envelope
-
-      //if(x>0.0f) { x -= od * x * x;  if(x < -V->env) x = -V->env; } //+= 0.5f * x * x; } //overdrive
-
-      //l += V->outl * x;
-      //r += V->outr * x;
+      if (x > 0.0f) {
+        x -= od * x * x;   //overdrive
+        if (x < -V->env) x = -V->env;
+      }
+      l += V->outl * x;
+      r += V->outr * x;
 
       V++;
     }
 
-    /*
     tl += tfrq * (l - tl);  //treble boost
     tr += tfrq * (r - tr);
     r  += treb * (r - tr);
@@ -377,35 +373,16 @@ void mdaEPiano::process(int16_t *outputs_r, int16_t *outputs_l, int32_t sampleFr
     l += l * lmod * lfo1;
     r += r * rmod * lfo1;  //worth making all these local variables?
 
-        outputs_l[v] = int16_t(l * 0xFFFF) >> REDUCE_LOUDNESS;
-        outputs_r[v] = int16_t(r * 0xFFFF) >> REDUCE_LOUDNESS;
-    */
-
-    outputs_l[v] = i >> REDUCE_LOUDNESS;
-    outputs_r[v] = i >> REDUCE_LOUDNESS;
-  }
-  /*
-    if (frame < sampleFrames)
-    {
-      if (activevoices == 0 && programs[curProgram].param[4] > 0.5f)
-      {
-        lfo0 = -0.7071f;   //reset LFO phase - good idea?
-        lfo1 = 0.7071f;
-      }
+    outputs_l[frame] = static_cast<int16_t>(l) >> REDUCE_LOUDNESS;
+    outputs_r[frame] = static_cast<int16_t>(r) >> REDUCE_LOUDNESS;
   }
-  */
+
   if (fabs(tl) < 1.0e-10) tl = 0.0f; //anti-denormal
   if (fabs(tr) < 1.0e-10) tr = 0.0f;
 
-  for (v = 0; v < activevoices; v++) if (voice[v].env < SILENCE) voice[v] = voice[--activevoices];
-
-  /*
-    for (v = 0; v < sampleFrames; v++)
-    {
-      outputs_r[v] = int16_t(o0[v] * 0xFFFF) >> REDUCE_LOUDNESS;
-      outputs_l[v] = int16_t(o1[v] * 0xFFFF) >> REDUCE_LOUDNESS;
-    }
-  */
+  for (v = 0; v < activevoices; v++)
+    if (voice[v].env < SILENCE)
+      voice[v] = voice[--activevoices];
 }
 
 void mdaEPiano::noteOn(int32_t note, int32_t velocity)

mdaEPiano.h

@@ -61,7 +61,7 @@ public:
 	  mdaEPiano(); // mdaEPiano(audioMasterCallback audioMaster);
 	~mdaEPiano();
 
-  virtual void process(int16_t *outputs_r, int16_t *outputs_l, int32_t sampleFrames);
+  virtual void process(int16_t *outputs_r, int16_t *outputs_l);
   virtual bool processMidiMessage(uint8_t type, uint8_t data1, uint8_t data2);
 	virtual void setProgram(int32_t program);
 	//virtual void setProgramName(char *name);
@@ -98,6 +98,8 @@ private:
   float Fs, iFs;
 
   #define EVENTBUFFER 120
+  #define EVENTS_DONE 99999999
+  int32_t notes[EVENTBUFFER + 8];  //list of delta|note|velocity for current block
 
   ///global internal variables
   KGRP  kgrp[34];