Post by gwenhwyfaer on Sept 20, 2007 12:45:15 GMT
I noticed this thread in the other forum, and - well, it's not quite right. The keytrack parameter is one I've tripped over in the past, because it's tricky and evil! So I thought it might be worth sharing my findings about how it really works, all learned the hard way...
Basically, as you know, the keytracking parameter has a range size associated with it - x semitones = 100%, for x = 1-100. It's also bipolar - middle C is always 0%, and every semitone below middle C is the negative of the corresponding semitone above. So when the keytrack range is set to '2 octaves = 100%': C1 = -100%, C2 = -50%, C3 = 0%, C4 = +50%, C5 = +100%.
The tricky bit is that in that case, C6 = +100% too, as does every note after C5 - because the range of the keytrack source is hard-limited to +/-100%.
So if, as suggested in the thread, you set "1 octave = 100%" for the keytracking range, and then a range of 12% for the filter mod depth - you get perfect filter / pitch tracking, but only for the two octaves around middle C. Which is probably not what's required.
To cover the whole keyboard range, one thing you can do is use "4 oct, 2 semi = 100%" for filter tracking (which will give a span of over 4 octaves either side of middle C, or over 8 octaves altogether) - that makes the filter tracking (0-100%) actually double its range, so you can easily get tracking of any fraction between -200% and 200% (so in that instance, I'd suggest a 4/2=100% with an additive filter mod, depth 50%).
In fact, unless you're absolutely sure it's what you want to do, I'd say there's never any point in using a range setting other than '4 oct, 2 semi = 100%'. It gives you full-keyboard coverage, it makes defining key-mapping tables easy (on the X axis, +1% = half a semitone up, and 0% = C3), and it gives a 200% keytracking range for any parameter.
Basically, as you know, the keytracking parameter has a range size associated with it - x semitones = 100%, for x = 1-100. It's also bipolar - middle C is always 0%, and every semitone below middle C is the negative of the corresponding semitone above. So when the keytrack range is set to '2 octaves = 100%': C1 = -100%, C2 = -50%, C3 = 0%, C4 = +50%, C5 = +100%.
The tricky bit is that in that case, C6 = +100% too, as does every note after C5 - because the range of the keytrack source is hard-limited to +/-100%.
So if, as suggested in the thread, you set "1 octave = 100%" for the keytracking range, and then a range of 12% for the filter mod depth - you get perfect filter / pitch tracking, but only for the two octaves around middle C. Which is probably not what's required.
To cover the whole keyboard range, one thing you can do is use "4 oct, 2 semi = 100%" for filter tracking (which will give a span of over 4 octaves either side of middle C, or over 8 octaves altogether) - that makes the filter tracking (0-100%) actually double its range, so you can easily get tracking of any fraction between -200% and 200% (so in that instance, I'd suggest a 4/2=100% with an additive filter mod, depth 50%).In fact, unless you're absolutely sure it's what you want to do, I'd say there's never any point in using a range setting other than '4 oct, 2 semi = 100%'. It gives you full-keyboard coverage, it makes defining key-mapping tables easy (on the X axis, +1% = half a semitone up, and 0% = C3), and it gives a 200% keytracking range for any parameter.
