Pulsar

Pulsar is built on Curtis Roads' pulsar synthesis. Each voice plays a train of short sound particles, called pulsarets, one per period, with silence in between. How often they fire sets the pitch. How long each one lasts sets the timbre. Because those are separate controls, the formants stay put while you play up and down the keyboard, a bit like a voice.

The fun part is the range. Slow the train below about 20 Hz and you hear separate clicks and pulses, so the synth becomes a rhythm machine. Speed it up and the pulses fuse into a tone. Sweep the rate and you can hear a beat turn into a note. Drop the keyboard a few octaves and a chord plays polyrhythms instead of harmony.

Up to three formants share each period, and a 16-step burst pattern or a random mask can drop pulses out of the train. That gives you everything from ticking clocks and drum patterns to vowels, buzzing leads and particle clouds.

Credits

• Curtis Roads, "Sound Composition with Pulsars", Journal of the Audio Engineering Society 49(3), 2001. The technique Pulsar is built on.
• Curtis Roads, Microsound, MIT Press, 2001, chapter 4.
• Alberto de Campo and Curtis Roads' PulsarGenerator (CREATE, UC Santa Barbara, 2001), the original pulsar instrument. Pulsar doesn't use its code or design, but it showed what the technique can do.
• Nathan Ho, "Pulsar Synthesis", 2022. A clear, practical write-up.
• Thomas Wilmering, Thomas Rehaag and André Dupke, "Pulsar Synthesis Revisited: Considerations for a MIDI Controlled Synthesiser", CMMR 2012. How to make pulsars play nicely on a keyboard.