>> Wishart describes in his book a technique he calls spectral focusing,

>> which relies on lpc. He says that lpc can be set to generate a filter
>> bank
>> which is distributed evenly with respect to pitch, but I’m not sure I
>> understand what he means and how it can be done in PD. lpc seems to
>> output
>> a set of amplitudes for the coefficients. Can I set the filters to
>> frequencies of my choice?
>>
Ah...LPC in PD.

I had a go at turning another speech processing system into a PD external with a view to being able to manipulate spectral envelopes and components about 5 years ago, but with no success. What LPC does is split the signal into filter coefficients and excitation - so that the excitation passed through the filter will reconstruct the original signal.

There is still no LPC plugin that really works in PD, and my attempt was glitchy and horrible. What would be better would be a pitch+noise separation process, such as is used by Spectral Modelling Synthesis by Xavier Serra at UPF in Barcelona. It is still available as part of the CLAM package ( http://clam-project.org/ ).

Perhaps the iem_spec library contains some useful FFT related stuff, but to be able to manipulate each frequency component individually is a formidable challenge!

Best,