[linux-audio-dev] XAP: Pitch control

Steve Harris S.W.Harris at ecs.soton.ac.uk
Mon Dec 9 17:31:00 UTC 2002


On Mon, Dec 09, 2002 at 09:37:20 +0100, David Olofson wrote:
> What I'm saying is simply that if *everything* in a standard, 12tET 
> net uses 12.0/octave, it doesn't matter whether you say you're taking 
> or sending note_pitch or linear_pitch - because they look exactly the 
> same. That way, *no one* pays the price for non-12tET - until you 
> actually want something to play using a different scale.

Right, but you do have to pay a price if you're not in 12tET, if you use
1.0 then theres never any price.
 
> > But the VST people were allready lumbered with note scale, that
> > puts them in a different situation.
> 
> You're probably right. The main thing they wanted to convince me of 
> was that you need *both* note pitch and linear pitch - but OTOH, that 
> was thinking in the terms of the rather primitive MIDI based, 
> effectively one-way event system of current VST.

Yes.

There are so few cases where note numbering is the right thing. The only
example we've come up with so far is non-ET arpegiators. Wow ;)

The differnce is that the VST/MIDI people are used to thinking of that as
the default case. I'm not.

> I don't think that's true. At least in "real" music, it's really 
> rather common to mix slightly "alien" scales with 12tET. Many 
> singers, violinists and other "continous pitch" people *deliberately* 
> tweak notes to make them fit better - although one might perhaps 
> think of that as something different from scales; not sure.

Yes, when I do this in synthesis I do it with signals applied to linear
pitch inputs. I guess you could do it by creating a novel tuning just as
well, but is that easier?

> AFAIK, there are even musicians that don't have much use of current 
> standard synths and applications, simply because they're too 
> restrictive, and/or way too cumbersome to deal with, when it comes to 
> scales and pitch control.

Yeah, like me. The answer is not to reenfoce the 12tET system.
 
> > Granted there will be people who want to run half
> > thier track in 12 and half in 7, but thats hardly a common case,
> > and we dont prevent it.
> 
> We don't? Well, lets hope that all Multichannel synths will do the 
> right thing when someone wants to play different scales on *the same 
> instance*.

They will as long as you dont try to enforce note numbering in the API.
Complex tunings wont map to note numbering in any useful way anyway.
If you just represent pitch, then I can create a virtual instrument
(connected to a physical one if neccesary) that can create the right
pitches for the scale (or be analogue).

As soon as I have synths that will only accept note numbers I'm screwed,
they wont accept the pitch data I want them to, the best I can hope for is
that a pitch->note converter wont screw it up too much.

I think this is better for unusual tunings, and it doesnt hurt the 12tET
case.

> Either way, scale conversions are lossless? When you're dealing with 
> *continous* pitch, you'll need either an exact formula, or you'll 
> have to use an approximation of some kind. We're not talking about 
> plain LUTs. (Pitch bend needs more than that, and continous pitch is 
> basically "pitch bend done right".)

OK, yes, I'l give you that. I cant remeber what the relevance was though
:) It does back up my point that pitch->note conversion is not ideal
though.

- Steve



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