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For many years I have been interested in microtonal music. One of my favourite composers is Harry Partch who developed an intonational system that used 6 notes chords (hexads) derived from both the harmonic and subharmonic series. The harmonic chords were reduced into a span of a almost an octave and a half rather than the 4 octaves that the chords would have spanned if they were not octave reduced. If this does not make sense, Partch's otonal (harmonic series) chords had the following ratios 1/1, 5/4, 3/2, 7/4, (2/1), 9/4, 11/4. If this chord was not octave reduced it would have the following ratios (in ascending order) 1/1, 3/1, 5/1, 7/1, 9/1, 11/1. Partch also used subharmonic chords which he called utonal (from the word undertone). The utonal chords are mirror images of the otonal (from the word overtone) chords. For the mathematically inclined the ratios are in descending order 2/1, 8/5, 4/3, 8/7, (1/1), 16/9, 16/11. Again if these chords were not reduced to an octave and a half span they would have the following ratios (and different order): 1/1, 1/3, 1/5, 1/7, 1/9, 1/11.
For more information regarding Partch's chordal structures see this page http://www.chrysalis-foundation.org/Partch-s_Diamond.htm

I am sure you are wondering what this has to do with the Doepfer A-100 system? Well, I currently use a Doepfer A-198 Trautonium-Manual / Ribbon-Controller with a Tubbutec microtonal CV quantizer. I feed the quantized CV to an oscillator and then send the oscillator audio to an Erthenvar patch chord module which has an Equal Tempered, just intonation, and Harmonic/Subharmonic modes. I use an doepfer A-143-1 to a quad vca for creating arpeggios from the chord outputs. While this setup is good, I wish to have the freedom to choose the chordal mixes available and to change them during performance. I believe that the A-113 subharmonic generator module may be able to do this. Does this module only do subharmonics or are harmonics also available? If the a-113 can only do subharmonics, can they be octave reduced ? Also is there a limit to the divisor (or multiplier if harmonics are possible). By this I mean is it possible to divide by 11, 13 or 17 etc ?

If the subharmonics cannot be octave reduced then is there another way to do this? Perhaps a precision adder or something could help?

Sorry for the long post

Cheers,

Justin

Doepfer

a-113 subharmonic generator

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