Voltage controlled arpeggiator (was Re: [sdiy] Design Process)

[David G. Dixon]

> I've been "back burnering" the idea of a voltage controlled arpeggiator
> lately, too.
> Was thinking something simple using an LM3914 bargraph driver with its
> outputs interfaced to some pots and a CV summer. Might be some
> interesting options available using the 3914 in "dot" mode and "bar" mode.
> "dot" mode - each step picks a voltage relative to 0V
> "bar" mode - each step "stacks" a voltage on top of the previous step.

Hey Oren, that's a very interesting chip!  And it comes in three versions
(linear, log, and VU meter).  I'm going to have to think about that in the
shower tomorrow!

The key for a VC arpeggiator (or, at least, the one I'm thinking of) is that
the CV must simply scan the steps in series, but each step must be
assignable to a distinct voltage.  It sounds like that's what you are
thinking of as well.  I'd like to be able to define arpeggio patterns
involving any number of chromatic tones within a two-octave range, and then
have that pattern repeat in higher bi-octaves.  How high the pattern would
repeat would depend on the setting of the CV input attenuator.  Also, how
the pattern would play would depend entirely on the CV waveform (a triangle
wave would cause arpeggiation up and down in uniform durations, a saw or
ramp would cause arpeggiation only down or only up, a sine would give
pleasing ritardandi at the top and bottom of the pattern, etc).  Also, I
will need a separate 1V/octave CV input which would tune the arpeggio from a
keyboard, so that the arpeggio pattern could be played in any key.  The
two-octave range is also critical, because I don't just want to be able to
play stock scale or mode patterns (phrygian, mixolydian, lydian dominant,
altered, etc), but I want to be able to arpeggiate fat jazz chords,
quartals, etc, and this requires two octaves.