Unison Detune - Analog or Digital?

[CutRock]

I'm mapping out my first big project, and have run into a bit of a hang up when it comes to how the detune will be handled. I figure I could probably have it incorporated into my voice allocation MCU so that the chip just outputs a distribution of pitches to each oscillator in unison, but I was wondering if it's common to use an analog alternative to this.

Thanks

[fengland]

so it sounds like you're building a polysynth with multiple oscillators per voice? that's very ambitious. But you could just have a little dc mixer on the pitch cv input of the second oscillators with control voltages coming from the voice allocation circuit and a detune knob connected to negative voltage.

[JovianPyx]

In a digital monosynth (4 osc), I have implemented variable detune and portamento by using two tuning tables instead of one.

In my case, the tuning tables are one semitone below standard and one semitone above standard.

I use linear interpolation to generate a specific tuning value from the two tables and a "selector" value. If the selector value is zero (assuming that it can also be either negative or positive) then the output value gives the "standard pitch" because it generates a value halfway between both tables. If negative, the note is flattened, if positive the note is sharp. The amount toward negative or positive controls the amount of detune.

Using this system, I can have NCO pitches close enough for a very slow phasing effect or they can be seriously out of tune or whatever else in between.

I also designed an 8 voice (4 osc per voice) polysynth that allows detuning oscillators using the same two table interpolation method. (I did not implement portamento in the polysynth). For this synth, the 4 oscillators can be detuned as much as a semitone in either direction. Additionally, an integer semitone value can be added to any oscillator. The two together can access any pitch the instrument can make. To get more range, I could put more distance between the tables.

this: http://electro-music.com/forum/download.php?id=24888 is a sample of this synth using ADSR controlled detune on all 4 oscillators.

I hope that helps.