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

[Tim Parkhurst]

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


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