Analog sequencers

[Christopher_List at Sonymusic.Com]

  > I myself am more of a fan of analog sequencers where
  > you can change the pitch on each step, in Semitones,
  > as oppossed to discrete pitches.
  [snip]
  > I don't know of any sequencers available nowadays like that,
  > except for the Doepfer MAQ machine.
  > Someday, I'll have my quantized sequencer finished.  :)  I need more
  building time.
  >
  > Ric

  A quantizer for a sequencer is REALLY easy. I've got one on a bread board
  right now that works great. You can switch it between semitone and whole
  tone quantizing. You can have it quantize a lot of different channels
  with only a few more parts/ channel. I'll work out a schem for y'all one
  of these days...

  Basic parts are (if I remember correctly - haven't touched it for about a
  month...) opamp setup as a relaxation oscillator, driving a 7 bit counter
  (CD2024) tied to the high bits of a DAC - I used the 14 bit (read:
  expensive) AD7245A - the output goes to an opamp set up for scaling and
  offsetting the stepped DAC output voltage. That's the core that provides
  a reference voltage in perfect 0.0833v steps.
  Then, for each channel you need a sample and hold - I used the cheap and
  available LF398 for simplicity - a nice fast opamp as a comparator and
  some caps and resistors.

  This method was described in detail by the likes of Juergen and Gene here
  last summer. It's very simple and elegant.

  There's some fine tuning involved - I will elaborate / post schem if
  there's interest..


  Re: Duane's Sequencer question-
  Who says you have to use it for playing pitches? It's great for adding a
  "cycled randomness" to things like filter frequency, noise volume,
  carrier frequency shifts of two FM'ed VCOs. Subtle stuff like that...
  Each knob set only slightly differently from the next. Think about how
  you'd play a lead if every note you played stepped your sequencer through
  one of 4 (or 8) steps that changed the <<timbre>> of your sound slightly
  for each step...

  - CList