Probabilistic Quantizer


Probabilistic Quantizer

I’ve enjoyed using the Turing machine clone for melody generation, but although it generates quasi-random sequences, when run into a standard quantizer the note frequency is essentially random. I came up with the idea for a quantizer that has a different probability for each note. This is the result. You set the desired relative probability of each note with the knobs and pull reset high to load the quantizer. The resulting probabilities are displayed by the graph on the right. You can also feed a gate in and get a random gate out. The gate probability is set by the gate knob.
The narrower and wider gates change the probability of each note by the amount set on the inc knob. Narrower moves all the probabilities toward even and wider moves them back toward the original setting. Due to rounding errors the final probabilities will fluctuate when triggering narrower repeatedly. Reset restores the original probabilities. The included file has a random array that will toggle the gates if the attached knob is greater than 0


Input Signal Range Notes
reset 0-1 a high resets the quantizer to the knob settings
narrower 0-1 a high moves the probabilities closer to even by the inc amount
wider 0-1 a high moves the probabilities closer to the knob settings by the inc amount
gate gate signal can be used to generate a random gate output
o 1 per octave signal

Output Signal Range Notes
gate gate signal random gate output
o 1 per octave signal


Control Function Notes
note probability knobs set the relative probability of each note
gate probability knob sets the probability that a gate will pass from 0 to 1
inc sets the increment for the narrower and wider gates from 0 to 0.1


There is a green light in the center of the knob for the active note when the output gate is active
The meter array at the right shows the current probability of each note from 0 to 1

Version History

Revision File Date Notes
2.1 Probabilistic Quantizer V2.1.audulus (44.2 KB) 01/21/2019 I removed the narrower, wider and random gate logic. I also moved the root to C instead of A.
1.0 random quantizer.audulus (496.9 KB) 01/20/2019 initial upload. Still a WIP


Revision File Date Notes
2.1 probabilistic quantizer V2.1.audulus (317.7 KB) 01/21/2019

I also put together a "lite: version that is simply a quantizer without the wider/narrower and random gate functions.
moved to main entry see above


I decided that the “Lite” version was potentially more useful than the original so it became V2.x. I left my earlier one for those that want to fool with it.

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I am delving into some of the probability/stochastic patches in the forum. This patch is very cool, but I am still a bit green in my Audulus understanding. Is the probabilistic aspect a result of the input signal as opposed to some randomness generated in the patch. Have I overlooked a Random somewhere in the patch?

It may be a bit mis-named. The original 1.0 version did have some internal probability generation with the gate, but I removed that logic in the final 2.x version to simplify the module. As you suspected the randomness is in the input to the quantizer. It could be a Turing machine module or my more recent QRST module or some other source of a random or quasi-random 1 per octave signal. The quantizer allows you to adjust the portion of each octave band which will resolve to a specific note. The knobs function in a similar fashion to the mask on a more traditional quantizer, but instead of fixed divisions such as semitones, change the crossover points in a continuous fashion. With a random signal into the quantizer, the knobs adjust the probability that a given note will play but the quantizer itself is deterministic. The same input with the same quantizer settings will always produce the same output.

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