Frequency Modulation Warp (FM Warp)

A short delay line whose read position is swept by an internal sine LFO. Crank the rate from a slow wobble to audio frequencies and the same control morphs from vibrato and chorus into full-blown frequency modulation — pitch warble, ring-mod-flavored metallic overtones, and grit smeared across whatever you feed it.

How it works

Your input is written into a tiny ring buffer, and an internal LFO continuously nudges where the buffer is read back. At low rates that moving read point is just pitch wobble — vibrato, then chorus as it widens. Push the rate into the audible range and the read position modulates fast enough to generate FM sidebands on the signal itself, turning clean tones harsh and clangorous. There's no feedback, so the effect stays focused on the source rather than building into a tail. The left and right channels run independent delay lines sharing the same LFO, with the right channel's phase offset set by the Width control, giving real stereo width even from a mono source.

Controls

  • Rate — speed of the modulating LFO, from 0.5 Hz up to 2000 Hz. Low is vibrato/chorus; high crosses into FM territory.
  • Depth — how far the read position swings, 0% to 100%. More depth means deeper pitch warble and stronger sidebands.
  • Mix — dry/wet balance. Fully wet at 100%; back it off to blend the warp under the original.
  • Width — stereo spread of the modulation between left and right, 0% to 100%. At 0% both channels wobble in lockstep for a centered, mono warble; around the midpoint they sit in quadrature for natural stereo; push toward 100% and they swing into anti-phase for a wide, hollow image.

Inputs & outputs

  • In L / In R — the signal to warp; patch mono or stereo audio.
  • Rate / Depth / Mix / Width CV — voltage control over each matching knob; patch an LFO or envelope to sweep the warp, swell the depth, fade the mix, or animate the stereo image.
  • Out L / Out R — the processed stereo pair.

Tips

  • For lush chorus, keep Rate low and Depth modest; for metallic FM tones, run Rate well into the audio band.
  • Patch an envelope or LFO into Rate to make the warp track each note or pulse with the rhythm.