format filter bank/string filter

[Martin Czech]

> hi all,
> I am looking into building a format or string filter for
> various vowel formats. I have the freq. of the required bands I would
> like to pass.
> 
> here is the question(s):
> are there any circuits posted for  this ( I think moog had such a filter
> bank)?
> any suggestions for simple active ( or passive) bandpass filters
> designs?
> 
You mean "formant", right ? What is a string filter?  Anyway,
I'd suggest a couple of state var filters, either in series
or in parallel. So you can adjust the magnitude, bandwidth
and frequency for each band separetely. Look into the second
formant (synth) book at Anders Sponton's. I got the link under
http://www.evenfall.com/diy/archive/index.html under diyers. It's
called RFM, resonance filter module.  You could of course also use
voltage controlled state vars, if you are going for vowels this could
be the right way, because a steady state vowel is boring and sounds
unrealistic, the "mixed" vovels like aii oii etc.  morph anyway between
two characteristics.

m.c.