I have for a long time wanted to get hold of some of the Radel electronic Indian Musical Instruments and mod them for use in a modular synth.
Cyndustries had some modules like this a while back. Anyway there is a big electronics industry in India,
so I figured there must be a few schematics out there for circuits that can simulate Indian instruments.
About the only one I found was an IEEE paper –
‘An Electronic Musical Instrument which accurately produces the spaces of the Indian Music’.
This circuit is based on the one in that paper although I modified it for use as an analogue synth module
to be driven by gates and CV rather than a keyboard.
I also included extra frequency divider outputs that can be fed to other filters for expanded sound range.
It is really a set of simple sub-modules working together.
A gate input controls a sample & hold, envelope generator and a VCA.
When the gate is high, a CV signal is fed to the VCO.
When the gate stops the S&H holds and the VCO sits on the same pitch.
A vibrato signal can be added to the CV input of the VCO which is independent of the S&H.
The output of the VCO
is fed to two frequency dividers,
one supplies 2nd, 4th, 8th and 16th divisions to transistor buffered outputs.
The other mixes these divisions and then feeds three signals into passive viola, violin and violino filters.
Pots can be used to adjust the level of each filter or just listen to one at a time.
The filter outputs go to a crude VCA which is controlled by an envelope triggered by the gate signal.
A pot can be used to set the rise and decay times of the envelope, another pot sets the gain of the VCA.