AVR-Chat

>> Right now, I've set:
>> TCCR0B = 0<<CS02|0<<CS01|1<<CS00 (no prescaling)
>> TCNT0 = 255 (overflow on next tick)
>> TIMSK=(1<<TOIE) (enable counter overflow int).

>    For one interrupt every 1/31250Hz, I'd use:
>    TCCR0A = 1<<WGM1  (CTC mode)
>    TCCR0B = 1<<CS01   (8MHz/8)
>    OCR0A = ((8MHz/8)/31250Hz)-1 = 32-1
>    TIMSK = 1<<OC1E0A
>    TCNT0 = don't care

I assume you mean 1<<WGM01 for TCCR0A (CTC mode, TOP=OCR0A).
I also changed ISR (SIG_OVERFLOW0) to ISR (TIMER0_COMPA_vect).
This works, more or less. That is, the interrupt routine gets 
called, but by the pitch I get it seems to be at a quarter of
the rate that it should be.

Strangely, altering OCR0A does not seem to influence
the pitch at all, which makes me think something else is
amiss which makes the ATtiny ignore the value in OCR0A.

Any ideas?

Best,
Marc