const int Output = 1;                                   // Can be 1 or 4
// Cater for 16MHz, 8MHz, or 1MHz clock:
const int Clock = ((F_CPU/1000000UL) == 16) ? 4 : ((F_CPU/1000000UL) == 8) ? 3 : 0;
const uint8_t scale[] PROGMEM = {239,226,213,201,190,179,169,160,151,142,134,127};
void note (int n, int octave) {
  int prescaler = 8 + Clock - (octave + n/12);
  if (prescaler<1 || prescaler>15 || octave==0) prescaler = 0;
  DDRB = (DDRB & ~(1<<Output)) | (prescaler != 0)<<Output;
  OCR1C = pgm_read_byte(&scale[n % 12]) - 1;
  GTCCR = (Output == 4)<<COM1B0;
  TCCR1 = 1<<CTC1 | (Output == 1)<<COM1A0 | prescaler<<CS10;
}


int cm[] = {0,3,7};
int fm[] = {0,5,8};
int g[] = {11,7,2,5,8};
int member = 3;
int note_length = 50;
int n = 0;
int octave = 1;
int akkord = 0;
unsigned long seconds = 0;
unsigned long prev = 0;

void setup() {
  // put your setup code here, to run once:
  //pinMode(1, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:

  note_length = random(30,70);
  octave = random(3,7);
  
  seconds = millis();
  seconds = seconds/1000;
  if (prev != seconds) 
    akkord = random(0,3);
  prev = seconds;

  switch (akkord) {
    case 0: // cm
      member = random(3);
      n = cm[member];
      break;
    case 1: // fm
      member = random(3);
      n = fm[member];
      break;
    case 2: // g
      member = random(5);
      n = g[member];
      break;
  }

  note(n,octave);

  delay(note_length);
}