LFOs: a periodic hand on the knob
Vibrato, tremolo, and wah are one mechanism — a slow oscillator turning a parameter, over and over.
An LFO is a low-frequency oscillator: the same object as lesson 1's oscillator, running below the rate at which the ear hears a tone. Its output never reaches the speakers. It is wired to a parameter instead, and its waveform becomes a hand turning that knob on a loop, at a speed and a distance you set.
The boundary sits near 20 Hz, the same one lesson 1 drew for hearing: below it you hear repetition, above it the repeats fuse into pitch. Most musical work happens well under that line — 0.1–1 Hz for slow sweeps of one to ten seconds per cycle, 4–8 Hz for vibrato and tremolo, 10–16 Hz for effects that begin to buzz. The toy below spans 0.1 to 16 Hz for exactly this reason.
The destination decides the effect
- LFO → pitch. A sine at 5–7 Hz swinging ±10 to ±30 cents is vibrato, close to what a violinist or a singer produces. At ±100 cents it becomes a siren. The toy reaches ±200 cents at full depth, a whole tone in each direction, which is well past musical.
- LFO → volume. A sine or triangle at 4–8 Hz is tremolo, the pulse of a vintage guitar amp. Depth matters more than rate here: a 3 dB swing shimmers, 12 dB is an obvious effect, and a square wave at full depth chops the sound into a gate.
- LFO → filter cutoff. At 0.2–1 Hz you get the breathing sweep behind most pad movement; at 4–6 Hz you get wah. The toy's filter destination swings ±2400 cents, two octaves each way at full depth, which is why the same depth number sounds far larger here than it does on pitch.
Shape and depth
The LFO's waveform sets the style of the motion. A sine spends most of its cycle near the middle and only touches its extremes, which is why it reads as smooth. A triangle moves at a constant rate and gives the most even sweep, which makes it the neutral choice for filter movement. A square jumps between two values and holds each one: on pitch that is a trill, on volume a gate. A sawtooth or ramp resets instantly, which suits a sweep that should restart rather than come back the way it went.
Depth sets how far the hand turns, and it is where most first attempts go wrong. Modulation you can point at is usually too much. A workable test: find the depth at which you first notice the sound is alive, then halve it. Depth is bipolar on Elektron devices, so a negative value runs the same shape upside down — silent on a free-running sine, obvious on a ramp or sawtooth, and the fastest way to flip a modulation that is fighting the sound.
Three shapes and the motion each one produces. The left column is the LFO's own bipolar output; the right column is the destination parameter, offset from wherever its knob is parked. Pitch swings both ways around the note, volume can only be pulled down from full, and a trill steps up and returns.
Rate in Hertz, rate in beats
A free-running LFO is set in Hz and ignores the song. That suits vibrato and tremolo, where the movement belongs to the instrument and not to the arrangement. It also drifts against the sequencer, so a repeated bar never lands in the same phase twice, which is what keeps a long slow sweep from sounding mechanical.
A tempo-synced LFO is set in note divisions, and the arithmetic is worth memorizing once. At 120 BPM a beat lasts 0.5 s, so one cycle per beat is 2 Hz. One cycle per bar of four is 0.5 Hz. One per eighth is 4 Hz and one per sixteenth is 8 Hz, fast enough to read as texture rather than rhythm. Elektron reaches these through two knobs: SPD sets the speed and MULT multiplies it, either against the current tempo or against a fixed 120 BPM. The manual's own advice is to try SPD at 8, 16, or 32 for straight beats.
The rate range on a log axis. Amber marks are note divisions at 120 BPM; the shaded band is the 4–8 Hz zone where pitch and volume modulation read as vibrato and tremolo. The dashed line at 20 Hz is where modulation stops being movement and starts being timbre.
One steady tone, one LFO, three destinations. Hold rate at 5 Hz and depth at half, then switch only the destination: the same motion arrives as vibrato, tremolo, and wah. Then park on the filter destination and walk the rate from 0.1 Hz to 16 Hz — below 0.5 Hz a slow sweep, near 5 Hz a wah, above 12 Hz a buzz sitting on the note. Last, find the depth at which each one stops being an effect and becomes part of the sound.
Each device carries this on its LFO / MOD pages, with far more reach than the toy above. The DEST menu holds 30 to 80 entries depending on the device and track type, covering nearly every parameter on the track — the other LFO's controls included, which is how one LFO ends up modulating another. SPD and MULT set the rate, WAVE offers seven shapes, and bipolar DEP is the depth. Two more are worth finding early: FADE eases the modulation in or out over the note, and MODE decides whether the LFO free-runs, restarts on every trig, latches its level, or runs one cycle and stops.