Interrupts and delay()

Using Arduino Programming Questions
9

Can you add a little code to toggle the on board LED after every delay and ( A ) check the time against the flashing LED and ( B ) comment out the calls to myTone() and myNoTone() and see does that restore the delay() to its proper duration?

I connected a LED to pin 6 of the attiny (PB1) and tried the following sketch:

#include <avr/delay.h>

void setup()
{
 DDRB = (1 << PORTB0) | (1 << PORTB1);
 PORTB = 0;

}

void loop()
{
  myTone(500);
  PORTB ^= (1 << PORTB1);
  delay(1000);
  myNoTone();
  PORTB ^= (1 << PORTB1);
  delay(1000);
}

ISR(TIMER1_COMPA_vect)
{
   PORTB ^= (1 << PORTB0); 
}


void myTone(int freq)
{
  float period = 1.00/(float)freq;
  float ticks = (125000.00*(float)period)/2.00;
  int over = ticks/255;
  TCCR1 = (1 << CTC1) | (1 << CS12); // divide by 8 prescaler
  
  
  OCR1A = ticks; //
  OCR1C = ticks; //
  TIMSK = (1 << OCIE1A) | (1<<TOIE1);
  
  sei();
}

void myNoTone()
{
 TCCR1 = 0;
 TCNT1 = 0;
}

the delays were still less than 1000ms, when I removed the tone functions the delays were normal.

Probably the interrupts are messing up with the delay()?