LFOs
An LFO (Low Frequency Oscillator) is an oscillator that's too slow to hear as a tone - instead, it's used to automatically wiggle other parameters back and forth. It's like having an invisible hand slowly turning a knob for you, creating movement and life in your sounds.
How They Work
A regular oscillator vibrates hundreds of times per second to create audible pitch. An LFO runs much slower, commonly around 0.1 to 20 cycles per second. You assign it to a parameter such as pitch, filter cutoff, or amplitude, and it moves that parameter through a repeating cycle.
LFO Shapes
LFOs use the same waveform shapes as audio oscillators, but each creates a different type of movement:
Sine
Smooth, continuous wobble. Its curved cycle is useful for gentle vibrato, tremolo, and filter sweeps.
Square
Instant switch between two values. Creates a "trilling" effect - think of rapidly alternating between two notes or two filter settings. Like a tremolo switch.
Sawtooth
Ramps up then drops back. Creates a repeating sweep effect - like an auto-wah that resets. Good for rhythmic filter patterns.
Triangle
Like sine but with straight lines instead of curves. Similar smooth wobble but with a slightly more linear, mechanical quality.
Random (Sample & Hold)
Jumps to random values at regular intervals. Creates robotic, glitchy, unpredictable changes. Classic sci-fi sound design and experimental textures.
Common LFO Targets
An LFO can modulate almost anything. Here are the most musically useful targets:
Pitch - Vibrato
Subtle pitch wobble. A sine LFO on pitch at low depth and moderate speed can approximate the periodic movement of instrumental vibrato.
Volume - Tremolo
Volume going up and down rhythmically. Think of a tremolo guitar effect or the pulsing of a Rhodes electric piano.
Filter Cutoff - Wah
The filter opens and closes rhythmically. Creates dubstep wobbles (fast), gentle tonal shifts (slow), or auto-wah effects (medium).
Pan - Auto-Pan
Sound moves left to right and back. Creates width and movement in the stereo field. Especially effective on hi-hats and pads.
The Two Key Controls
Rate (Speed)
How fast the LFO cycles. Slow rates (0.1-1 Hz) create gentle evolving movement. Fast rates (5-20 Hz) create vibrato, tremolo, or wobble effects. Very fast rates can create new timbres entirely.
0.1 Hz = one cycle every 10 seconds (slow evolution)
1 Hz = one cycle per second (gentle motion)
6 Hz = a common vibrato-rate starting point
20 Hz = intense wobble, enters audio range
Depth (Amount)
How far the LFO pushes the parameter. Low depth = subtle, barely noticeable movement that adds life. High depth = dramatic, obvious modulation that becomes a defining feature of the sound.
Low depth on pitch = subtle vibrato
High depth on pitch = siren / sci-fi effect
Low depth on filter = subtle tonal shift
High depth on filter = dramatic wah / wobble
Production Tip
Try subtle LFO movement when a sustained synth patch feels static. Add a sine LFO to the filter cutoff at very low depth and a slow rate (0.2-0.5 Hz), then adjust the amount until the tonal change supports the part without distracting from it.
Try it
Hear the same sustained note with three different LFO targets.
An LFO is one motion source, but each target changes the result.
Key takeaway
LFOs add cyclical movement to any parameter - volume, pitch, filter cutoff, and more. They create vibrato, tremolo, filter sweeps, and wobbles. Rate and depth are your main controls.
Next: the finishing touches - reverb, delay, chorus, and other effects that add space and character.
Add movement to your sounds
Starts generates parts you can import into your DAW and experiment with LFO modulation.