Voltage-Controlled Oscillator (VCO)

A band-limited analogue-style voltage-controlled oscillator. It tracks 1V/octave pitch and puts out sine, triangle, sawtooth, and square waves all at once — the core voice for basses, leads, drones, and anything that needs a clean, tuneful tone.

How it works

The saw and square are generated with PolyBLEP correction, which rounds off the hard edges just enough to suppress the digital aliasing you'd otherwise hear as gritty high harmonics — so it stays crisp and musical even up high. Pitch follows 261.63 Hz · 2^(V/oct + Freq + Fine), i.e. middle C with the knobs centred.

Controls

  • Wave display — drag left/right to sweep coarse pitch, up/down to set the square's pulse width.
  • Freq / Fine — dial pitch in precisely: Freq sets coarse tuning in octaves, Fine trims ±100 cents.
  • FM / PWM — attenuverters for the modulation inputs. Centred is off; turn either way to scale depth, counter-clockwise to invert.
  • LFM — chooses how the FM input behaves. Off is exponential FM, which stays in tune; on is linear FM for clangorous, bell-like, metallic timbres.
  • Soft — sets the sync mode. Off hard-resets the phase on each sync pulse for a hard, aggressive lock; on reverses phase direction for softer, smoother sync sweeps.

Inputs & outputs

  • V/Oct — 1V/octave pitch; patch a keyboard or sequencer here to play it.
  • FM — frequency-modulation input, scaled by the FM attenuverter and shaped by the LFM switch.
  • PW — pulse-width CV for the square output, scaled by PWM.
  • Sync — locks the oscillator to another source; the Soft switch sets hard or soft sync.
  • Sine / Triangle / Saw / Square — the four waveforms, all live simultaneously. Only the square responds to pulse width.

Tips

  • Patch a second oscillator's output into Sync and detune this one with Freq for classic hard-sync screams.
  • Flip LFM on and feed an audio-rate source into FM for inharmonic, FM-synth-style tones; leave it off when you need FM that stays in tune.
  • Modulate PW with a slow LFO for a thickening, chorused pulse-width sweep on the square output.