History
I have played around for years, here are some of my early attempts.
Small PIC based digital oscillator with VCA, but no filter.
Moog ladder filter board.
Small High Speed digital oscillator waveshape type thing.
Early digital oscillator board.
My first real attempt at a TB-303.
Schematics
This was basically a high speed input divided down with flip flops. There were 256 waveforms out, the first 16 way switch selected which harmonics went into the mix. The second selected the amplitude of some of them. So you could get squares, saws and pretty well any combination of odd harmonic waveform in between. I guess it was a poor mans walshbank or wavetable synth. Not the most inspiring, but fairly reasonable once passed through a filter. This lead into the various digital oscillators I then tried and wavetable synthesis.
Using a PIC as a high speed oscillator and generating a 6 bit digital sawtooth waveform. This was not the best sounding sawtooth and the PIC ran out of steam at 5KHz. So I decided to have another go, but using the R-2R network as a programmable current source and then just gate it digitally. I did this thinking it was a highly original design. Then I found out it was not at all new and Roland had done it years earlier !