Sequencer idea/quandry

[WeAreAs1 at aol.com]

POLARIS at VAX1.Mankato.MSUS.EDU asked:

<< Would it be reasonably feasable to construct a sequencer that was a series
of sample-and-holds, so that one could step through the sequence entering
notes directly from a keyboard instead of dialing in pots?  >>

I can't imagine how you would ever get those sample-and-hold's to keep from
drooping.  Even modern very high-impedance buffer amps have a certain amount
of current leakage, which would cause the held voltages to slowy drop down.
 Hmmm.. does anybody have any specs on the reliable hold time of a good hi-Z
sample and hold circuit?

One thing that can help an analog sequencer in this regard is the addition of
a voltage quantizer.  It's found in at least a couple of different commercial
analog seq's.  (ARP sequencer, Polyfusion, I think the Oberheim
Minisequencer...any others?).  You'd still have to enter all the notes from a
pot, but you wouldn't have to painstakingly tune each and every note.  The
quantizer would round all sequencer voltages off to the nearest half-step,
allowing you to more quickly set up sequences.

Hmmm... maybe the aforementioned sample and hold input idea would be able to
hold the memorized voltage longer (long enough?) if you quantized their
outputs to the nearest half-step.  That way, they would have to droop more
than halfway down to the next lowest pitch before you would hear any pitch
change.  For that matter, it might even be possible to regularly poll the
*output* of the quantizer, and then use this re-sampled voltage to "refresh"
each sequencer step's sample-and-hold.  However, by the time you got halfway
done designing, building, and debugging such a circuit, you would likely be
telling yourself "You know, MIDI's not really such a bad thing, after all..."

There's a very interesting quantizer circuit that you can check out at Josh
Brandt's website.  It's the Elektor Music Quantisizer.  It allows for
programmable sets of quantization values, such as smoothly changing voltage
inputs being quantized to a pentatonic scale, or to any series of arbitrary
note sets.  Has anyone on the list built one of these?

Here's Josh's URL:   http://www.ultranet.com/~mute

Mike B.