[sdiy] analogue phase modulation

[Eric Brombaugh]

On Jan 9, 2007, at 10:06 PM, Adam Schabtach wrote:

>> What amount of (maximum) phase modulation depth (number of
>> periods), do typical
>> digital PM sounds a la DX7 etc. have ?
>
> Chowning's original paper has several examples; the maximum depth for
> several non-percussive instruments is 4 or 5, and 10 or 25 for bell 
> and drum
> timbres. The parameters in a DX7 are all in arbitrary units so the 
> maximum
> depth used in that implementation isn't readily apparent but obviously
> someone knows what it is since it's been reimplemented in software by 
> Native
> Instruments and others.
>


When I was doing the Modcan VCDO research I found that 314% mod index 
was enough (funny - that number looks familiar). Any more than that 
didn't sound sufficiently different to be worth the reduced resolution 
at the low end of the range. The number may seem a bit low compared to 
the Chowning values quoted above but we get some pretty nice bells out 
of that module.

Eric