Oscillators

SQR

A hollow square VCO at 50% pulse width. One knob, one input, one output.

What is a SQR?

A square voltage-controlled oscillator at fixed 50% pulse width: one knob, one input, one output. Squares contain only the odd harmonics of the fundamental (1, 3, 5, 7...), declining at 1/n - the same harmonic recipe as a triangle but much louder in the upper harmonics. Hollow, woody, "clarinet-like" character. Anti-aliased via polyBLEP. The square-only sibling of the full VCO; reach for that if you need pulse-width modulation, FM, or sync.

In a patch

Classic for sub-bass (one octave below a saw lead), chiptune-style melodies, and hollow lead voices. Patch a sequencer or quantizer into V/Oct for melodies; SQR out into a VCA shaped by an envelope. Square waves through a filter give a darker, more vocal tone than a saw - fewer harmonics for the filter to chop, but the ones that survive are mathematically pleasing (only odds). Layer a SQR sub-bass under a SAW lead at the same pitch for vintage video-game-soundtrack vibes. The TUNE knob (+/-24st) sets the octave/interval at V/Oct=0V; default is C4 (261.6Hz).

Inputs

V/Oct (cv) — Pitch input. 1V = one octave (1V/Oct standard). 0V = C4 (261.6Hz), 1V = C5, -1V = C3, etc. Patch a sequencer (SEQ8 row out), a quantizer, or a MIDI-In CV to play melodies. Add to TUNE: at TUNE=0, V/Oct=1V plays C5; at TUNE=+7, V/Oct=1V plays G5. Negative voltages drop pitch below C4.

Outputs

SQR (audio) — Square output at 50% pulse width, +/-5V audio. Anti-aliased via polyBLEP. Only odd harmonics, declining at 1/n - hollow, woody, "clarinet-like" character. Same harmonic series as a triangle but with much stronger upper harmonics, so it sounds buzzier than a triangle but hollower than a saw. Classic for chiptune leads and hollow sub-bass.

Controls

TUNE — Tune in semitones. Range +/-24 (two octaves up or down). Sets the pitch when V/Oct is 0V (default = C4 = 261.6Hz). Linear semitone scale - matches the full VCO's coarse knob exactly.

Inspired by

The square-only sibling of the full VCO with pulse width locked at 50%. Squares contain only odd harmonics, falling off as 1/n - the same harmonic recipe as the triangle but louder, hollower, and with the woody character of a clarinet. For pulse-width modulation, reach for the full VCO.

Doepfer A-110-4
Moog 921 (square voice)

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