[linux-audio-dev] XAP: Pitch control

I was in this long thread about pitch control on the VST list, and I think I learned a few things. (For a change! ;-D) There are times when continous, linear pitch (what I have in Audiality) is perfectly fine - and in those cases, it's by far, the simplest possibly way you can control pitch of a synth. You get note pitch, pitch bend, continous pitch control over the whole range, whatever scales you like and all that, using *only a single pitch->frequency conversion* somewhere in your synth code. I will bet almost anything that there simply cannot be an easier way of dealing with this. *However*, in some cases, you may not be all that interested in the actual pitch, but rather just want to deal with the notes in whatever scale the user wants to deal with. One example would be a simple, basic arpeggiator. Sure, you *could* do that with linear pitch, but then the plugin would have to either assume that you want 12tET (or whatever), or you need a way to tell it what scale you want to use for the output. (Note that the kind of arpeggiator I'm thinking about here may be expected to generate a full, modulated chord from a single note, so it can't just look at a full input chord and pick the exact pitches from that.) In that case, you'd much rather have input more similar to integer MIDI pitch, and *possibly* pitch bend to go with that. This could indeed be expressed as "linear pitch" as well (float; 1.0 per octave), but with one very important difference: it would actually be 1.0 per *note* - where what a "note" is is not strictly defined or known to the plugin. The plugin just assumes that the user knows what 0-4-7 means, if he/she enters that for "arpeggio offsets". The plugin also assumes that the user will put a suitable note_pitch to linear_pitch pitch converter in between the output and the synth, or that the synth understands note_pitch events. Note that linear_pitch = note_pitch * (1.0/12.0) for 12teT, so these "conerters" (or note_pitch support) can be very trivial to implement. If you want "weird" scales, it gets slightly more complicated, but the *major* point here is that no synth plugin is required to do this - and still, every synth plugin can use any scale! (How many VSTi plugins actually support non-12tET scales? ;-) 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? //David Olofson - Programmer, Composer, Open Source Advocate .- The Return of Audiality! --------------------------------. | Free/Open Source Audio Engine for use in Games or Studio. | | RT and off-line synth. Scripting. Sample accurate timing. | `---------------------------> http://olofson.net/audiality -' .- M A I A -------------------------------------------------. | The Multimedia Application Integration Architecture | `----------------------------> http://www.linuxdj.com/maia -' --- http://olofson.net --- http://www.reologica.se ---