Absolute genius, I’m going to have to experiment with this. I’ve been looking for a way to emulate the KV100 pulser as an effect, too, so this may be an easier way to get that effect either through MIDI triggering or with an audio to midi plugin driving it. Could be useful for other modular instruments like Voltage Modular or VCV.
Also, I think I misspoke about polyphonic input when I meant complex frequencies, so let me walk it back a bit. It’s a complex idea, so bear with me.
A monostable multivibrator works by alternating between a stable (off) state and an unstable (on) state, with the duration of the unstable state making the pulse output. Pulse width isn’t determined by the input at all, but by a separate timing circuit with a potentiometer to adjust the width.
The basic circuit is a transistor pair acting as switches with a resistor capacitor timing circuit controlling the width. The Metasonix KV100 (and the TM-1 this circuit comes from) uses a dual triode, so the circuit function is the same but the edges of the pulse are a bit dirtier due to tube characteristics, so a perfectly on/off pulse ends up sounding too digital.
In operation, the input signal acts as a trigger input; when it crosses the threshold, it turns one half of the triode “on”, triggering the unstable state. While the circuit is in the unstable state where the pulse output is high, any additional incoming input triggers are ignored until the pulse cycle ends and the circuit reverts to its stable state. Once the circuit is stable, the next incoming trigger will start the process again.
So with a monophonic input that has a clear fundamental or defined pitch, the pulser behaves fairly nornally as you’d expect, tracking the pitch input. The hardware has limits due to its design, however, and there are 2 cases where (un)wanted noise on the pulser input could be contributing to some of the more unique parts DOOM sound.
For instance, with a 50Hz sine wave, you expect fixed pulses at 50Hz intervals. But when that sine wave’s pitch exceeds the maximum pulse width, the pulser will create a dissonant output in an attenpt to track a pitch beyond its physical limitations.
EDIT: Accidentally posted too early, I’m on moble.
Adding noise does this. Increasing harmonic content does this. And Mick used a sine wave with white noise and added a bunch of harmonics with distortion.
With your method, even using direct MIDI input, do you think there would be a way to mimic this instability?