linear detuning works !

[Haible Juergen]

For those who followed the thread about linear (constant rate)
detuning in exponential VCOs:

*** Proudly presenting: ***

The capacitive divider thing works very well.
I modified a SEM VCO (clone) with a 150n / 1n divider, and injected
a 0 ... 1.5uA constant current (manually controlled by a potentiometer
and
a 10Meg resistor).
It fullfills all my expectations: Precise detuning from 0 to 1Hz with
constant 
beat rate over the keyboard. Combine this with the normal detune knob,
and
you get everything from constant rate to a rate increasing with factor 2
per octave.
Only a few components involved, worth less that one dollar.
Believe me, once you have heard this, you want it all the time!
I have drawn a little schematic. Mail me if you want it, or if you want
to put it to some archive.
Though I have tried it on a SEM VCO, it should work on almost every
sawtooth-based VCO, so it's a possible modification for many synths.

JH.