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

[thx1138]

On 6/5/09 4:55 PM, "Tom Wiltshire" <tom at electricdruid.net> wrote:

> 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
>> 
> 
> 
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Hi Tom,

When I was working at E-mu many years back we implemented a
Hard-Sync/Soft-Sync on our Analogue VCO Module platform.

I should look this up and see if this was true and post it up to you guys.

Regards,

Terry Shultz