dsp blog for xoxos.net

unison voicing

with 2 comments

a very brief entry on unison voicing, as i’ve just finished another unison oscillator and coincidentally been asked a question. this should be useful to anyone experimenting with modular synthesis who hasn’t developed much familiarity with dsp yet –


for unison voicing gain, i use 1 / sqrt(# of voices), making:

1 voice: 1 / 1 = 1.0 gain

2 voices: 1 / sqrt(2) = ~.7071 gain

4 voices: 1 / sqrt(4) = .5 gain

this seems to give about the same volume no matter how many oscillators you stack together 🙂

other note on unison voicing is to avoid equidistant spacing between pitches – there’s a spectral analysis graphic in the manual of my ‘horizon’ unison synth that clearly illustrates this concept –

equidistant pitch (logarithmic scale, of course) between three or more oscillators (of course) is going to produce cyclic phase cancellation and pronounced beating, instead of the smooth, thick detune effect. pointedly, equidistant pitch is useless 🙂

i use a simple n*n nonlinearity crossfaded with equidistance as a ‘spread’ parameter – try using a hi-res spectral analysis (voxengo’s SPAN has longer fft block rates which give better frequency resolution) then use sine oscillators and exaggerate your detune amount.. if the frequencies are the same distance apart, you will hear phase cancellation/beating.

there are different effects you can achieve, eg. bunching the pitches towards the center is different from spreading them away from the center.. things to experiment with 🙂

horizon has several stereo voice distribution schemes.. after using horizon for ?? three years now ?? i almost never used the left>right or right <left schemes, which pan in order of lowest to highest pitch – the highest pitch will draw the most attention, so this strongly weights the stereo image… i left them off the new build.

i did find it useful to have a mode where voices are split between either the left or right channel (i include an option to alternate which channel receives the highest pitch, usually in patching, if i use both oscs in unison mode, the highest pitch of each osc will be towards the opposite side) and another mode where voices are panned lowest to highest from the center to the side, alternating back and forth.

both of these modes sit better in the mix for some sounds.. the split is “cleaner” and the center>side distribution makes a thicker timbre (obviously).


Written by xoxosvst

August 10, 2011 at 5:55 am

Posted in Uncategorized

2 Responses

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  1. horizon is an amazing and underrated synth and it’s nice to read about the ideas behind it. It’s just a shame it seems to suffer from the same kind of instability that most elaborate SE creations suffer from and a shame it doesn’t work on Mac ;-). If you’re interested in making a new native version, i would like to help you port it (or something similar) and show you how to use IPlug. Got all the MSVC projects and whatnot sorted down to a tee, it’s super easy to use once you know how and way more powerful than synthedit.

    I know i’ve tried to convert you before and failed, but i thought id have another go. 🙂


    Oli Larkin (@olilarkin)

    August 13, 2011 at 12:40 am

    • cheers oli – i deeply appreciate the offer 🙂 i’d really like to use the steinberg sdk directly with fclt, i’m very reluctant to use cv++ express or another sdk as my sdk experience is limited to win32 and SE. i’d prefer as few intermediaries as possible. it’s possible i’ll reevaluate this stipulation, lol

      i really need to run out of ideas that are viable in the SE sdk so i can focus on switching. at present, i’m considering building each voice separately to circumvent jeff’s velocity smoothing.

      as a sidenote, i was just reading this analysis of the “original” unison voicing, and amused to learn it suffers from the issue discussed above – each pair of successively lower and higher pitches have the center pitch as intermediary, producing some degree of phase cancellation :/

      it’s analysis of the supersaw leaves little to the imagination.


      August 13, 2011 at 2:09 am

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