[sdiy] A potential problem with a voice-assignable organ

[Tom Wiltshire]

I think you're right, Tim. There has to be some kind of sync signal  
to keep things in phase. I can't see any other way you could do it.

T.

On 5 Jun 2009, at 22:13, Tim Parkhurst wrote:

> On Fri, Jun 5, 2009 at 1:43 PM, Tom  
> Wiltshire<tom at electricdruid.net> wrote:
>> Hi All,
>>
>> <snip>
>> My voice-assignable clone, however, uses different processors for  
>> each note,
>> so if you played an octave, you'd get two different processors  
>> playing two
>> different Cs.
>> Given that the 16' waveform of the higher note is the same pitch  
>> as the 8'
>> waveform of the lower note, what's to stop them being completely  
>> out of
>> phase?
>> If this happened, large parts of the sound would disappear.
>>
>> Since we're talking about a digital system, this isn't going to be  
>> rich,
>> lush beating between different oscillators - just two out of phase  
>> signals
>> cancelling.
>>
>> How would one get around such a difficulty? I'm finding I can't  
>> let go of
>> the idea until I've worked it out completely...
>>
>> Thanks,
>> Tom
>>
>>
>
> Hi Tom,
>
> How about a "sync" signal from the top octave down to the lowers?
> Since you're not going to have too much drift between the octaves, the
> sync signal wouldn't need to be constantly monitored (so it probably
> wouldn't need to be an interrupt). Maybe only needed on a key press,
> or whenever the processor has a few spare cycles. Also, if you did
> implement a sync signal, you now get the option of purposefully
> introducing a controlled phase shift or beating between octaves.
> Should only need one pin on each processor.
>
> Then again, this is all from a guy who is definitely NOT a programming
> expert. ;-)
>
>
> Tim (needs to be constantly monitored) Servo
>
>
> -- 
> "Sire, the church of God is an anvil that has worn out many hammers."
> - H.L. Hastings
>