Low-frequency oscillator

▸What it is

An LFO is an oscillator that runs slow enough to feel — typically below 20 Hz — and is used as a control signal rather than an audible tone. Routed to filter cutoff it creates a slow wah; routed to pitch it creates vibrato; routed to amplitude it creates tremolo; routed to pulse width it creates the classic shimmer of a fattened square. The shape matters: a sine LFO is smooth, a square is on/off, a sample-and-hold is random steps. Rate decides how fast it moves, depth how far. The LFO does nothing on its own — it only matters once it is routed to something.

▸Questions

• What is a good LFO rate for vibrato?

  5–7 Hz feels natural — close to a singer's vibrato rate. Slower than that becomes drifting; faster sounds nervous.

• Should I sync the LFO to tempo?

  For rhythmic effects (filter wobble, dub-style chops) yes. For vibrato and breath, free-running is more natural.

• How is an LFO different from an envelope?

  An envelope is triggered by each note and runs once; an LFO runs continuously and shapes whatever it is modulating in cycles.

▸In the curriculum

First taught

PD3 · Motion — Assign a slow LFO to the filter cutoff. Part of the Pad track.

Reused in

The same concept comes back in 1 lesson later in the curriculum, in a new context.

▸Related concepts

Concepts that share a lesson with low-frequency oscillator: