xr2206

[Sean Costello]

At 11:21 AM 11/15/96 AST, you wrote:
>I've already posted this to Bert Schiettecatte (sorry that you'll recieve
>this message twice).
>
>The xr2206 is a very fine sine generator (THD,total harmonic distortion is
>smaller dan 1% I believe).
>It has an am and fm modulation input, especially the fm input is very cool.
>I think aphex twin used a similar device on ventolin (I care because you do
>cd) the tone in the beginning that deformes to one big noise.

I think that the noise in "Ventolin" is made as follows:  A low-pass filter
is used (MS-20?  I haven't heard an MS-20 enough to tell - I don't even know
if the MS-20 filters can self-oscillate), with the resonance increased to
the point of self-oscillation; this is the "dog whistle" sound heard at the
beginning of the track.  A drum machine (no idea what sort - I know very
little about techno, x0x boxes, etc.) is run through distortion, and into
the input of the filter.  The filter's cutoff is also being modulated by the
drum machine signal (probably boosted so as to be acceptable as a CV).  This
gives the burbling sqaggly sounds of the main drum track; when there is a
drum sound, the sine wave/Filter cutoff is modulated to get a strong FM
sound; when there is no drum sound, the filter resonance goes to the
original sine tone.

Apparently most of the distinctive Aphex Twin drum sounds are made using
normal drum machines, run through distortion and then into a filter, with
varying degrees of audio rate FM on the filter.  It may be simple, but it
still sounds cool to me.

Sean Costello