Psych Tone in Javascript

J. Donald Tillman
December 2018

This is a software simulation of the Don Lancaster's Psych Tone that runs in a browser.

The Psych Tone was an early electronic music algorithmic composer and synthesizer presented in the February 1971 issue of Popular Electronics Magazine. It uses a 6-bit Linear Feedback Shift Register, to produce a repeating pseudo-random sequence up to 63 notes long. Three taps are made off the shift register, those are weighted, and summed to drive a Voltage-Controlled Oscillator to produce a pitch. Then an envelope is applied.

The Psych Tone is incredibly rare. It was a complex project, not many people built them, and it is difficult to find a working unit today. And that's a shame, because this was a remarkable device and we can learn much from it. So I recreated the Psych Tone in software, from the schematics, so it can be appreciated.

Instructions

Hit the PLAY switch to get it started.

The VOICE SELECT switches choose a waveform. The schematic in the article labels them "sawtooth", "peaked sawtooth", "spikes", "clipped", "sine wave", and "overdriven".

The TUNE SELECT switches select three inverted or non-inverted bits off of the shift register. These binary values are summed in weights set by the RATIO pots to form pitches. These are usually not chromatic pitches.

The UP/DOWN switch choose between an XOR and XNOR function for the feedback. (Note that UP will get stuck if it hits state 111111 and DOWN will get stuck if it hits state 000000.)

The BACK/FRONT switch chooses different feedback taps, FRONT for the last two taps, BACK for the first and last.

STEP/GLIDE turns the envelope on and off.

PITCH, TEMPO, VOLUME, SUSTAIN, ATTACK, and DECAY do the obvious.

The PAUSE SELECT switches require those corresponding bits on to produce a sound, for rests. All switches off is all rests.

Catalog Page

References