[linux-audio-dev] XAP status : incomplete draft

David Olofson david at olofson.net
Mon Dec 16 16:47:01 UTC 2002


On Monday 16 December 2002 12.36, Steve Harris wrote:
> On Sun, Dec 15, 2002 at 09:12:55 +0100, David Olofson wrote:
> > > > I don't get it. If you're supposed to place the scale
> > > > converter *first*, then how are you supposed to be able to
> > > > apply anything like traditional music theory, rather than
> > > > pure, continous pitch based theory? You will have to know the
> > > > *exact* temperament of the scale (to decode the input, and to
> > > > generate output in the same scale), even if you're only
> > > > worried about notes.
> > >
> > > That holds true for per-note descriptions too. The only way you
> > > can improve in it is with *extensive* scale metadata. Which we
> > > dont have and dont plan to have.
> >
> > You're still missing the point. Note pitch is <something>/note,
> > which is a linear scale. With 12t, it's identical to 12tET. This
> > is very easy to process.
>
> No, you're still missing the point ;)
>
> What you said is only true of 12tET, and (as we know)
> 12tET<->octave conversion is trivial and reversable.

How can it be true for 12tET only, when the whole point with note 
pitch is that it *is* ET, at all times, regardless of what scale it 
maps to?

Operating on the linear form of something is not always equivalent to 
performing the same operation on the transformed form. When you have 
a scale converter, it's NOTEPITCH input is *linear*, and it's PITCH 
output is *transformed*.

Now, how can it possibly be irrelevant whether you're operating on 
linear or transformed data in this particular case? Or; what 
invalidates all processing of linear data, just because it will be 
transformed later?

I must have missed something in the math classes. :-)


> As soon as you have not ET scales you will have to either:
>
> 1) include lots of standardised scale metadata

What would you use that for?


> 2) use pitch anyway (or no other processor will understand your
> 'note' data)

Yeah - and include reverse and forward scale converters in every 
plugin that needs to do this kind of stuff?


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

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