Wanna build an analog CV harmonizer?

[Don Tillman]

Here's an interesting idea I just came up with.

It involves an analog shift register.  (I think Serge makes one of
these; it's sort of like a bunch of S/H's in a row with a bucket
brigade like action.  Typically they're driven with a keyboard control
voltage and clocked off the keyboard trigger to provide the last N
keyboard notes played.)

Imagine that you have an 8-stage analog shift register running off the
keyboard as above, and another circuit that uses a feedback (digital)
shift register arrangement to pseudo-randomly select one of the analog
shift register outputs (ie., one of the past eight notes played).
This will effectively be a real-time analog harmonizer playing notes
from the same scale as you are playing.

         +----------------+
CVin-----|                |
         |analog shift reg|
trig--+--|                |
      |  +----------------+
      |   | | | | | | | |
      |   | | | | | | | |
      |  +----------------+
      |  | 1/8 analog mux |-----> harmonized CV out
      |  +----------------+
      |       | | |
      |       | | |
      |   +-----------------------+
      +---|psuedo random shift reg|
          |        3 taps         |
          +-----------------------+

A second pseudo-random tapper could provide a third voice.

An extra cool feature could be added at the output: a comparator would
sense if the control voltage is below some middle level, and if it
does, add an extra octave worth of CV (1.0v) to the harmonized CV out.

  -- Don