// MIDI
byte channel = 1;
byte instrument = 0;
byte velo     = 127;  //velocity of MIDI notes, must be between 0 and 127
// random notes
byte Rnote = 0; // note by random
int Rlow = 50;  // random range low for notes
int Rhigh = 80; // random range high for notes
// play timing
int TNON =950;  // time play note ON
int TNOFF =50;  // time play note OFF
// midi commands 
byte MCMD = 0;  // midi command called status byte = command + channel
static byte basis = 127;
static byte NOFF = basis;
static byte NON = basis + 16;
static byte PAT = basis + 32; 
static byte CMC = basis + 48;
static byte PCR = basis + 64; // program change request = 191 + channel
static byte CAT = basis + 80; // + channel
static byte PBC = basis + 96; // + channel  Pitch Bend Control

//____________________________________________________________________
// send MIDI message ( USB )
void MIDImessage(byte Mcommand, byte Mnote, byte Mvelo) {
  Serial.write(Mcommand);    //send note on or note off command 
  Serial.write(Mnote);       //send pitch data
  Serial.write(Mvelo);       //send velocity data
  Serial.println();          // we write only pseudo MIDI
}


//____________________________________________________________________
// SETUP
void setup() {
  Serial.begin(115200);
}

//____________________________________________________________________
// MAIN
void loop() {
  Rnote = byte(random(Rlow,Rhigh));
  MCMD=NOFF + channel;
  MIDImessage(MCMD,Rnote,velo);
  delay(TNON);
  MCMD=NON + channel;
  MIDImessage(MCMD,Rnote,velo);
  delay(TNOFF);  
}