[linux-audio-dev] XAP: Pitch control

David Olofson david at olofson.net
Mon Dec 9 08:54:01 UTC 2002


On Monday 09 December 2002 14.42, Steve Harris wrote:
> On Mon, Dec 09, 2002 at 01:45:22PM +0100, David Olofson wrote:
> > Hmm... As to having a synth support *both* note_pitch and
> > linear_pitch controls, I suppose that would effectively just be a
> > dual interface to a single internal control value. Send something
> > to linear_pitch, and it goes directly into the internal pitch
> > variable. Send it as note_pitch, and it gets multiplied by
> > (1.0/12.0) or is passed through an interpolated "weird scale"
> > table first. Makes sense?
>
> I think it makes sense to just standardise on 1.0 per octave for
> all pitch values, that is relevant to most (all?) scales and as you
> pointed out the conversion to 12 tone per note maths is trivial.
>
> For an apregiate in 12 tne you just add 1/12 per semitone, not 1.0,
> I dont think thats hard.

Well, yes - but did you get the actual point; that linear pitch may 
not be all that useful to plugins that don't care about the details 
of your scales?

I suggested on the VST list that linear pitch is all you need, but 
was proven wrong, more or less. At least, I now think that it makes 
sense to allow plugins to think in terms of notes rather than 
continous, linear pitch, since that relieves those plugins of the 
burden of having to know about the scale in use for the input, to 
"reverse engineer" the input data, and then convert back to the 
desired scale on the outputs.


//David Olofson - Programmer, Composer, Open Source Advocate

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