toneInterrupts.ino

int tonepin = PORTB1;

void setup() {
  // put your setup code here, to run once:
  DDRB = _BV(tonepin); //Set up tone pin as output

  TCCR1A = _BV(COM1A0); //Mode will be CTC; WGM12 is in B register
  TCCR1B = _BV(WGM12) | _BV(CS11); //Set up x8 prescaler
  OCR1A = 0x1000;

  interrupts(); //Enable interrupts globally
}

void loop() {
}