[sdiy] Speaking of the Elektor Vocoder (and the Korg Vocoder)
richard at skydancer.com
Wed Feb 20 19:22:37 CET 2008
On 20 Feb 2008, at 17:01, anthony wrote:
> I suppose a filter-bank could be thought of as a crude or coarse
> FFT. The more and narrower the filterbanks the more it would come
> to approximate an FFT - maybe in this case FT. Well actually, doing
> it analog, it's sort of instantaeous.
It sort of isn't, because the envelope followers have a time constant.
> But I wonder if the transfer function of a bunch of filter banks
> has the same math behind it as the actual Fast Fourier Transform,
> which as I understand it, is a recursive algorithm.
No, and no.
Digital filters use a weighted delay matrix with feedback paths
(sometimes with some non-linear distortion) and work on a continuous
stream of data.
The FFT is a windowed function which works on blocks of data,
transforming them in place.
There's no reason why you couldn't code a continuous high-quality
1024 way digital bandpass filter bank. It might even be more
musically useful for some applications. But it would have different
time domain characteristics to a phase vocoder FFT, and would very
likely sound somewhat different too.
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