I just added 5 more outputs to my MOTM 120
2003-01-17 by Richard Brewster
The MOTM 120 Suboctave Multiplexer is a cool module
for audio processing. I've found a way to use it for control voltage
generation too. I DC-coupled the main output so it works with all
input frequencies. LFO inputs can produce a 16-step sequence for
controlling a VCO pitch, all adjustable with the internal mixer. I used
the extra panel space to add five new outputs. There is a pulse output for
each of the four suboctaves. These outputs are +/-5V for
invertibility. I can use them to gate envelopes at different stages in the
sequence. The fifth output is a fixed-level weighted mix of the four
suboctaves, range 0 to about +6V. This produces a staircase wave of
16 equal steps when only the A input is used. The cross-product with
the B input can produce very interesting patterns. All the new outputs
have audio frequency application, as well. This is a simple circuit with
just three TL072 op amps (though it does entail a bunch of wiring).
Why would I do this? Well, I am one of those
oddballs who does not intend to use a keyboard controller. I am in
search of patches that do interesting semi-random things. So I am after
sources of stepped voltage to generate pitch sequences, when I am in the
mood for "notes". In this same vein, I am planning to build one of Ken
Stone's Infinite Melody modules, enhanced with an internal clock and noise
source. If you're a DIY type, you should check out Cat Girl
Synth.
One day, after I get the full MOTM module
complement together and start discovering what it can do, I might just enter one
of those "aleatoric" composition contests.
-Richard Brewster