Oscillators

TRI

A mellow triangle VCO. One knob, one input, one output. Soft-edged and warm.

What is a TRI?

A triangle voltage-controlled oscillator: one knob, one input, one output. Triangles contain only the odd harmonics of the fundamental (1, 3, 5, 7...) but they fall off as 1/n^2 - much faster than a square or saw. The result is a mellow, woody timbre that sits somewhere between a sine and a square. Anti-aliased via integrated polyBLEP, so it stays clean across the full pitch range. The triangle-only sibling of the full VCO; reach for that if you need FM, PWM, or sync.

In a patch

Patch a sequencer or quantizer into V/Oct (1V/Oct), TRI out into a VCA shaped by an envelope. The triangle's soft harmonic content makes it a natural lead voice that does not need much filtering - it already sounds polite. Two TRI modules detuned a few semitones (e.g. one at +0, one at +0 with V/Oct from a different sequencer) layer beautifully. Triangles are also a great FM modulator (in the full VCO's FM input) - less harsh than a sine modulating at audio rates, more musical than a saw. 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

TRI (audio) — Triangle wave output, +/-5V audio. Anti-aliased via integrated polyBLEP square with DC blocking. Only odd harmonics, decreasing as 1/n^2 - mellow, woody. Use as a soft lead voice, an FM modulator (less harsh than a sine), or layered under a brighter saw/square for warmth.

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 triangle-only sibling of the full VCO. Triangles have only odd harmonics (like a square) but they fall off as 1/n^2 instead of 1/n - mellower, less buzzy. A natural choice for warm leads or for layering under a brighter saw.

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

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