DSPs for converting guitar signal into synthesizer waveforms?

I am interested in getting synthesizer tones out of guitars. I have accomplished this with plugins / pedals that use midi conversion but its always just a little bit off tracking wise. However, I got this pedal that is not using any conversions, just manipulating the signal to the point where it sounds synthy.

I want to be able to organically modify the guitar signal with an audio plugin that will convert the shape of the guitar signal into something like a square wave without using midi conversions.

What dsps should I use? Where should I start? Any ideas on how to do this?

For a start you could try hard clipping the signal with lots of gain (basically a comparator) so it becomes square-ish, then run that through a VCF and VCA. Use an envelope follower on the original signal to get control signals for the VCA and VCF, or use it to trigger one or two ADSR envelopes.

Some other creative things you can try, out of the blue:

  • Create a “2nd OSC” one octave up by full-wave-rectifying the input and also running it through a comparator
  • Differentiate the square and discard negative edges to get a unipolar needle pulse, run through a highpass to remove DC bias, integrate to get a saw wave
  • Add a modulated delay to one of the “OSCs” to get a detune-ish effect