[sdiy] My two cents on sequencers

[Peter Grenader]

The question (for me) is what should the ideal analog sequencer do.
Start/Stop/Reset/Pulse outs per stage/Pulse out per step/Seq Up/Seq
Down/Pendulum/Portamento/Hard sync (pulse IN per stage)/CV out....and CV in.
This is the one that so many don't approach, yet became (for me anyway)
about the most useful functions among them.  The Buchla's did it, the Serge
still does (TBK)the Doepfer MAQ kind of does it and Grant's Wiard definately
does it...the ability to assign the direction of travel not by a switch, but
by a voltage.  

Where this comes in very handy is generating arbitary voltage strings -
patterns in which the user assigns the voltages, but allows the system to
assign their order. Imagine putting a random voltage into this CV input.
You set the string of voltages, and the sequencer replays them randomly.
Very useful when generating rythmic lines ala Mort Subotnick's Sky of
Cloudless Sulfer.

One method to do this is using a string of window comparitors or a 3914 to
assign the output based on the amplitude of the input.  Works welll, but
gets a little choked up when you wish to repeat the same step over and over.
You have to pull some tricks to get the device to recognize a repeating
input level. 

I have built one that does this and Analog Systems is currently working on
finishing it based on that design.  You can use the outputs of the window
comparitors to drive the output pots (sequencer) - or I've also used them to
turn on CMOS switches which in turn gate the common signal from a Doepfer
keyboard controller board.  This allows an analog device to create midi
on/off messages that vary in pitch based on the amplitude of the input.  So,
I can generate any of 20 midi notes based on the input signals amplitude (20
divisions between 0 to 12 volts.  Works like a charm.

I'm rambling here...but you should all look into the handy feature for
sequencer design.  It's the bomb.

ok, lemme have it,

Peter