OpenCL-based ChucK UGens would definitely be interesting...
On Sat, Dec 12, 2009 at 3:14 PM, Hans Aberg
On 12 Dec 2009, at 19:32, Kassen wrote:
Do these track the overtones? - When checking the spectrum of an oud, I noticed that the fundamental is missing if one passes to new note by shortening the string with the finger against the board without striking it with the other hand.
Well, fft as such doesn't "track" anything.
In a past thread, when discussing using GPUs for getting extra computing power, I forgot to mention this FFT that achieves 144 Gflop/s on the now not so new GeForce 8800GTX: http://en.wikipedia.org/wiki/OpenCL
Haven't looked at details, but I think it can be used as just an added parallel computing resource.
All you get is energy and phase for a certain band over that frame. From this we can quite easily determine the most prominent frequency, but as you know that need not be the fundamental. It quite likely is the fundamental for many signals but we don't *know* this and without more knowledge about the piece we can't say what the root of a certain chord is, even if we could manage to separate the notes. Pitch trackers often get very confused by chords (and may output all sorts of musically interesting "garbage" in response).
What we can do -given enough frequency resolution- is try to find a series of harmonics and use that to calculate what the fundamental must have been. Harmonics will be integer multiples of the fundamental, after all. This is what our hearing psychology does when listening to something like your oud.
Actually, the cochlea produce difference tones which do not exist acoustically. And if the input is a harmonic series with missing fundamental, it will be restored by that.
So one idea might be to add such difference tones as a part of an analysis.
Hans
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