[music-dsp] The shape of filters & interaction between them

[Eli Brandt]

Martin Eisenberg wrote:
> I once saw a paper on bandpass filters with nonzero magnitude at
> Nyquist, which can be used to make high-frequency peaks less skewed.
> Unfortunately, I don't remember the author or title, and I can't find
> the paper even though I was sure I kept it. Does anyone know what
> publication I'm thinking of?

One paper on this has a title you might might overlook a hundred times:
"Musical Applications of New Filter Extensions to Max/MSP".
http://cnmat.cnmat.berkeley.edu/ICMC99/abstracts/new-filters.html
> For "biquads~" we have implemented an unusually general model
> integrating recent theoretical work on parametric equalizer
> design. Five parameters can be adjusted; the boost/cut peak frequency;
> the bandwidth (specified in octaves); the reference gain at DC; the
> boost/cut gain; and the gain at the bandwidth edges. The gain at
> Nyquist frequency doesn't drop to 0 dB as with conventional digital
> parametric equalizers, instead the frequency response closely matches
> an analog parametric equalizer with these design parameters.

Pictures and a bit of discussion, too:
http://cnmat.cnmat.berkeley.edu/~tristan/Resume/parameq.html

Ah, says the technique is from a Orfanidis paper in AES '96, "Digital
Parametric Equalizer Design with Prescribed Nyquist-Frequency Gain".

-- 
     Eli Brandt  |  eli+ at cs.cmu.edu  |  http://www.cs.cmu.edu/~eli/