hi all ... im developing a funky wavetable synth thats inspired by the sequential circuits prophet 2000 from 1985. it uses the original 12 bit ROM from this synth and and a synthesis menthod called harmonic aliasing.

• all frequencies and repeat rates are related by simple integer relationships
• adaptive just intonation = infinite tuning systems
• 3 oscillators per voice
• wavetables by multiplexing oscs with waveshaped sines
• variable sample rate simulation via resampling with audiorate wavetables (BLITs)
• integrated complex numeric sequencer
• integrated delay for hardware mixer feedback loop with analog eqs

basically it includes everything i think is cool about numeric sequencing and is still really low on dsp because its all based on integers mechanics like early wavetable synths.

this synth can sound really ambient or real raw depending on the complexity of the number relationships and the waveshaping settings. eventually this is going to be a hardware synth with FPGA technology, variable sample rate per oscillator and analog eqs/filter ... just like in the 80s

project logo:

https://i.imgur.com/F1kqrMt.png

prototype patch:

https://imgur.com/XpxKxA3

wave multiplexing:

https://imgur.com/O2Ze6a1

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harmonic aliasing is inspired by a patch by acreil: https://forum.pdpatchrepo.info/topic/6759/new-anti-aliasing-and-phase-distortion-abstractions.

early discussion: https://forum.pdpatchrepo.info/topic/11176/adaptive-sample-rate-and-harmonic-aliasing-in-pd

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mixer delay feedback loop feature:

lots of different sounds with audiorate waveshaping:

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@lilakmonoke Hi! Sounds very good to me. I am looking for a low-cpu synth for my rpi 1, will you ever share your work?

Thanks!

@lilakmonoke Very nice! I'd also be interested in your method of harmonic aliasing as well as in the original 12 bit roms of the prophet, if it's something you'd care to share.

hi folks, thanks for the kind comments!

sure ill share the patch eventually but right now its an uncommented messy laboratory affair. best thing you can do right now is look at the patch image above which is quite self explanatory.

here is the vs rom in one wav file, scan this in 128 chunks of 128 samples and you have the single wave data.

vsallwaves.wav

harmonic aliasing is best described by acreil in the above mentioned blog post because thats where i got the idea from. the rest is trial and error and a lot of listening to integer combinations.

harmonic aliasing is actually my own term for what im trying to do. here is how i would describe it:

• if you repeat 128 samples with a phasor at 128 hz (or 64/32/16/8/4/2) or any multiple of 128 your phasor restarts exactly at the beginning of the wave data and the aliasing frequencies generated by the steppyness of the data will follow the harmonic overtone series 1,2,3 etc. depending on the multiple.

• if you introduce another prime divider ie. 3 as in 128 / 3 the phasor will line up with the sample data every 3rd sample and the osc will alias at the 3rd subharmonic frequency which will be somewhat more disharmonic than any overtone.

• another way to look at it would be the pattern repetitions. at subdivision 5 the phasor starts at 5 different points in the sample data and its easy to imagine that the readout patterns are all slightly different ... but the whole thing cycles after 5 phasor rounds = 5th subharmonic..

• if you subdivide 128 further with a higher prime ie. 563 you will get 562 different sounding samples until nr. 563 lines up again. get the idea?

this is all very easy to hear once you experiment with prime subdivisions and multiplications. just remember its all based on synching the data flow from the sample with the frequency of the index phasor. this will work with ANY sample data, the vs rom is just cool to use for vintage synth fans.

whats important for proper aliasing is that you use a simple [tabread] into the data without any interpolation like tabread4 or oversampling!

all the other elements in the synth like delay, waveshaper, sequencer follow the same rule as they are just repetition devices like the wavetable oscillator.

if you finally synch everything to the sample rate of your soundcard the voltages that hit your speakers will repeat in exact patterns. thats the idea of this synth: precision number repetition controlled by harmonic/disharmonic integer combinations ... just like the great 80s synths waldorf microwave or prophet vs.