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

[cheater cheater]

But you define the chords in an arpeggiator by holding down multiple
keys on the keyboard - I'm not sure what you mean - do you just want
to hold one key and select a chord with some sort of interface?

D.

On Tue, Feb 16, 2010 at 18:46, David G. Dixon <dixon at interchange.ubc.ca> wrote:
>> You've just described a multibit ADC
>
> Yes.  In fact, what I'm thinking of is a kind of quantizer, but one where
> the binary number is further processed through logic to add the intervals.
> For instance, say you wanted to make a full dominant 13 chord.  The notes
> (relative to major, and numbered from the root) are 1, 3, 5, b7, 9, #11, 13,
> 1....  The intervals (in half-steps) are 4-3-3-4-4-3-3-....  Now, a typical
> quantizer will produce the following intervals: 1-1-1-1-1-1-1....  Hence,
> the logical operation here involves adding the correct binary numbers to
> each output in order to obtain each successive output.  In this way, any
> number of intervals can be activated or deactivated over a given range.  For
> example, if one only wanted the sus 4 chord, one would require 1, 4, 5, 1,
> 4, 5, 1....  The intervals are 5-2-5-5-2-5-....  Hence, one would have to
> add 4-1-4-4-1-4 to the output of the ADC before latching back into the DAC.
> In this way, it doesn't matter to the quantizer how many intervals there are
> or how widely spaced apart the notes of the arpeggio are.  It is simply
> going up and down a certain number of steps as determined by the CV
> attenuator.  It also doesn't particularly care on which step it starts the
> pattern.
>
> Now all I have to figure out is how to implement that logic efficiently.
>
> For the more musically inclined among you, the way I would actually use this
> thing is to have two oscillators; one playing a bass note, and the other
> playing the arpeggio.  In this way, the bass note (which is optional) would
> not have to be part of the arpeggio.  This frees the arpeggiator up to play
> shells and upper structures over a two octave range, giving very rich
> harmonic textures.  For example, if another oscillator is playing 1 (an
> octave down), then the arpeggiator could be playing 3, b7, b9, #9, #11.  The
> overall range of the chord is more than two octaves, but separating out the
> root (or deleting it) gives more flexibility.  It also allows the bass note
> to be changed (in this case, perhaps, to #4 in order to obtain the tritone
> substitution) without reprogramming the arpeggio.
>
> Now, of course, what you'd really want is to be able to program the arpeggio
> in digitally and change it in real time, or even from the keyboard.  One
> could even have a dedicated mini-keyboard which acted as the switch bank for
> this device.  With that, one could play broken chords almost as if one had a
> polyphonic synth.  With a couple of analog shift registers (particularly my
> new and improved ones, which are damn-near perfect) operating at high clock
> speed and driving several oscillators, it would almost be like having a
> polyphonic synth.  Hmmm... better take another shower...
>
>