I would like to be able to adjust the pitches of individual notes accurately so that I can get GPO to play in temperings other than equal-temperament, especially to be able to play "pure" intervals and chords. So I need to be able to adjust the pitches with an accuracy better than what the ear can hear -- say to within a cent (a hundredth of a semitone) either way.
I am thinking so far of inserting a pitch-bend (pb) event at the beginning of each note. The resolution of pb data is quite good enough, but it would need to be entered by hand into an event list because graphical methods or a pitch wheel would not be precise enough. A slow process, but that's OK.
I have a few questions I hope someone can help me with. Indeed any comments or advice would be welcome.
* The manual is a little vague on the subject of pitch-bend. I think it says +/- 2 semitones for most instruments and +/- 6 for the trombone. But is this exact? My initial experiments, based on listening only, suggest to me that pb=+8191 is exactly 2 semitones for the instruments I tried, except for the trombone which sounded off to me. Is it possible to get proper data on this?
* Is the range linear? That is, if pb=8192 does correspond to 2 semitones, does pb=4096 correspond to one, pb=2048 to a quarter tone, pb=410 to one cent and so on?
Perhaps I should modify that a little, since I would guess that is extremely unlikely that the relationship is absolutely linear. So: is it linear enough, that is, linear to within say a couple of cents either way over the necessary range of a semitone either way?
* What about the intonation of the instruments in the GPO library as it stands? Is it just my ears or are some of the samples a bit off? (Flute Plr1's A3 for instance.)
What's on my mind here (in case it isn't obvious already) is that with an instrument like GPO we can have our cake and eat it too -- we can have the ability to modulate freely and at the same time have pure intervals and chords, that is, just intonation relative to whatever the temporary tonal centre is. I find that very exciting.