10 Dec
2002
10 Dec
'02
4:44 p.m.
On Tuesday 10 December 2002 14.48, Nathaniel Virgo wrote:
On Monday 09 December 2002 11:40 pm, David Olofson
wrote:
How would that make anything easier?
I would be happy to see a clean solution for
this, but so far,
these are the only alternatives we have managed come up with:
1. 1.0/note for note_pitch, 1.0/octave for linear_pitch.
Converter plugins required everywhere, even for 12tET.
Even 12tET-only hosts have to handle this.
2. 1.0/octave for linear_pitch, no note_pitch (?).
Host calls required for conversions. Plugins have to
find out what scales senders are using, or who is
sending what. How does this work if multiple senders
send to the same Channel?
3. 1.0/note for note_pitch, 12.0/octave for linear_pitch,
No conversion needed for 12tET. Converter plugins can
be used when other scales are desired. There cannot
be 12tET-only hosts, since scales are not a host side
matter.
More ideas, anyone?
4. Raw frequency in Hz. It's only with ET scales that an exp() function
is used to convert
from the scale into the frequency,
Wrong. Linear pitch, as used by synths, is <some value>/octave, and
that's all there is to it.
When dealing with scales, you take one form of pitch control - be it
MIDI note numbers + pitch bend, or *Continuos* Pitch (1.0/note for
example) - and express the note pitches as Linear Pitch, Hz
Frequency, or whatever.
Linear Pitch is just a mathematically handy way of expressing
frequency.
[...]
If you want to transpose by one 12tET semitone, just
multiply by
the twelfth root of two (about 1.0595).
Although of course for modulating by lfos etc the exponential will
still need to be performed somewhere, so my preference is actually
2.
Exactly. That's why I don't think Hz frequency belongs in the API at
all. You'll do better with linear pitch most of the time, and when
you finally reach an oscillator that wants period or frequency, it's
easy enough to calculate it.
I think that insisting on an exta factor of 12 would
be a bad,
bad, bad, bad mistake.
Agreed. It's just that all other solutions seem to be just about as
bad. :-(
Not only would it lead to extra work in a
great deal of cases, but you are bound to get people casting it to
an int, which would destroy the whole purpose of having it
continuous in the first place.
Where does the int cast get in...?
If the factor of 12 is there in
some places but not others, that's an unnecessary complication
which will lead to a loss of generality since the two different
types of signal can no longer be interchanged.
Yes. So let's have 1.0/note for continous pitch (corresponds to MIDI
pitch + pitch bend, sort of; this is *before* you apply scales),
1.0/octave for linear pitch (absolute relation to Hz), and then...
we'll have to convert continuos to linear at some point. That's the
disadvantage; you *have* to actually convert. (Well, unless you're
thinking in terms of one tone/octave.)
Pros with scale converter plugins:
* They are just plugins, and can do *anything*.
* Any host can host them - no need for explicit scale support.
* New scale converters can be used directly with any host.
Can someone suggest alternaties and advantages with those?
//David Olofson - Programmer, Composer, Open Source Advocate
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