The CGS gate sequencer is really the second part of the interface between the organ and the synth, though it can be used for other things.
What I needed was a way to sequence the gate pulses I had derived from the organ's rhythm unit. I had the remains of an old hard drive tester lying around, so that was cut up to give me the top and bottom rows of switches and the row of LEDs. The center row of switches were salvaged from a prototype speech synth, and also have a center off position.
The top and bottom rows each have two outputs, one giving a gate signal for the full length of the sequence step, the other output being gated with the incoming clock signal for a shorter pulse.
The center row has only a single output, but the switches allow either gated or full length pulses to be selected.
There are two inputs, clock, and reset, which I drive from the divided clock and downbeat signals I have derived from the organ.
An eight position rotary switch allows sequence length to be selected.
The circuit is essentially a 4017 with support circuitry, a huge diode/switch matrix and a few AND gates and inverters to deal with the resultant signals.
And Emily is on the panel again.
- Gate Sequencer for music synthesizers. (archived) by Ken Stone, 2000, with permission of the author
- CGS Synth discussion group, for discussion of locating parts, modifications and corrections etc.