maths for noise added to frequency for analog modeling

Dario's icon

I'm trying to find the proper maths to add bits of noise to the frequency of an analog modeling type synth. Namely so when I add this noise to the freq (say between -.1 and +.1) it changes the pitch of the synth the same amount whether the frequency is 55 or 440. I think I need to use logarithmic scaling or something but not positive on how this would work exactly

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Roman Thilenius's icon

you can use mtof for that kind of thing. start working linear, then add that to notenumbers, then mtof.

Dario's icon

Thanks Roman. I tried that but its still sounding off. It works well when I throw a snapshot in there but of course i wanna get it all in signal rate

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Floating Point's icon

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Roman Thilenius's icon

noise~ *~ mtof~ ... all available for signal :)

Christopher Dobrian's icon

I suggest using the noise signal as an exponent with a base of 2, and use that as a multiplier to vary the fundamental frequency. In that way, when the noise ranges from -1 to +1, it will cause a pitch variation of ±1 octave, whatever your fundamental frequency. Divide the amplitude of the noise by 1200 if you want to be able to represent pitch variation in cents. The rand~ object provides linearly-interpolated noise, with a new random value chosen at whatever rate you specify.

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Dario's icon

mmmmm!! sounds perfect thank you!!!

Dario's icon

I'm trying to build Chris's solution in Gen but for some reason its coming out all wacky. I think there's a problem with the pow object in Gen... or at least how I'm using it. It works great in MSP but... I like building everything in Gen too :D

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Roman Thilenius's icon

the MSP pow object has the inlets reversed (compared to the max object), that might be the case for gen, too.

Dario's icon

k Ill try that. thanks!

Dario's icon

nope that didnt work