ATtiny85-note-play.ino

#include<avr/io.h>

const int Output = 4;                                   // Can be 1 or 4

const int LED = 1;

// 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;
}

void Beep() {
  TCCR1 = TCCR1 | 3;                      // Counter = clock/4
} 

void NoBeep() {
  TCCR1 = TCCR1 & ~3;                     // Counter stopped
}

void setup() {
  pinMode(Output, OUTPUT);
//  pinMode(LED, OUTPUT);
  // Setup beep
  TCCR1 = 1<<CTC1 | 0<<COM1A0 | 0<<CS10;  // CTC mode, counter stopped
  GTCCR = 1<<COM1B0;                      // Toggle OC1B (PB4)
  OCR1C = 189;                            // Plays 1042Hz (C6)
//  digitalWrite(LED, HIGH);
}

void loop() {  
  for (int n=0; n<=12; n++) {
//    note(0, 4);
    Beep();
//    note(0, 4);
    delay(500);
    NoBeep();
//    note(0, 0);
    delay(500);
  }
}