[chuck-users] pitch tracking in ChucK

[mike clemow]

OpenCL-based ChucK UGens would definitely be interesting...



On Sat, Dec 12, 2009 at 3:14 PM, Hans Aberg <haberg at math.su.se> wrote:
> 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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