elena
Developer
Posts: 17
Posts: 17
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Post by elena on Apr 6, 2018 20:24:29 GMT 1
Hi, as a premise, I'm a very beginner with SE, I just downloaded the demo (I will decide whether to register) just because for some research purposes I needed to experiment with some audio processing ideas which unfortunately no VST around (AFAIK) allows me to do... so I have to write mine... or at least I'm trying...
I am pretty trying to implement a simple audio processing FX where a delay time on the incoming signal is modulated by the MIDI note (for example, doing that on a white noise can generate interesting sounds).
The big obstacle I'm facing is that the pitch voltage coming out the MIDI TO CV is linear of course (well... apparently it is 1 V / octave with an offset I have still to figure out - a voltmeter connected there sumply goes nuts even within a container and with MIDI TO CV set to MONO), but to properly control the delay time (in ms) this value has to be properly offsetted and then converted to an exponential value, in order for the sound produced by the delay to be musically consistent. I could not find any conversion tool within the builtin modules. The only one which could apparently do an useful job was the Float function but it has serious drawbacks: first of all, it needs the voltage signal to be converted to float first of all (and then perhaps back to voltage), but the conversion operator only works at few Hz. So I suspect this is definitely not the way to go. Any suggestions ? How can I properly convert the pitch signal to a suitable exponential (after offsetting if needed, of course) ? Thanks
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Andrew
Developer
Posts: 110
Posts: 110
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Post by Andrew on Apr 6, 2018 20:56:54 GMT 1
Pitch is not linear, it's logarithmic. Ironically you actually need a linear frequency aka in Hertz or kHz and then calculate the period in milliseconds.
So -> Pitch to kHz (Frequency) and then -> kHz to time ( Time = 1 / Frequency )
Cheers
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elena
Developer
Posts: 17
Posts: 17
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Post by elena on Apr 7, 2018 12:09:28 GMT 1
Hi, I know pitch is logarithmic, but the so called "pitch" voltage coming out the MIDI TO CV is actually a linear signal, it linearly maps to keys even if it is called "pitch", that's not my fault lol. The MIDI TO CV does not offer any actualy frequency output afaik. Anyway, in the meanwhile I could solve perfectly the problem by a very smart usage of the Waveshaper2 module, with some math skills, and in one night of work I could test and assemble my perfectly working midi controlled delay fx module. Works great Thanks to SE
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Andrew
Developer
Posts: 110
Posts: 110
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Post by Andrew on Apr 8, 2018 8:20:57 GMT 1
Hi, I know pitch is logarithmic, but the so called "pitch" voltage coming out the MIDI TO CV is actually a linear signal, it linearly maps to keys even if it is called "pitch" Hehe, probably just depends on how you see the math, but it boils down to the same thing. For me, frequency(linear) is mapped logarithmically to get pitch. To get back to linear(frequency), you use -> Pitch to frequency = Middle_A * pow(2,pitch-5). (might be "-0.5" depending on scale). If you are interested, what you are actually doing is called Karplus-Strong synthesis(if I understand correctly), there is some fun variations out there on the net. Glad you got it working! A little bit of math knowledge will get you a long way with SE. Cheers
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