LFO

A Low Frequency Oscillator (LFO) produces a slow oscillation that modulates audio parameters over time. Connect an LFO to gain for tremolo, frequency for vibrato, pan for auto-pan, or filter cutoff for auto-wah.

Basic Usage

import { createLFO, createOscillator } from 'ez-web-audio'

const synth = await createOscillator({ frequency: 440 })

// Tremolo — modulate gain at 5Hz
const tremolo = createLFO({ frequency: 5, depth: 0.3, type: 'sine' })
tremolo.connect(synth, 'gain')
tremolo.start()

synth.play()

Connecting to Parameters

An LFO can modulate any audio parameter on sounds, oscillators, effects, PolySynth, and GrainPlayer:

// Vibrato — modulate frequency
// Filter sweep on an effect
import { createFilterEffect } from 'ez-web-audio'

const vibrato = createLFO({ frequency: 6, depth: 50 })
vibrato.connect(synth, 'frequency')

// Auto-pan
const autoPan = createLFO({ frequency: 0.5, depth: 0.8, type: 'triangle' })
autoPan.connect(synth, 'pan')
const filter = createFilterEffect('lowpass', { frequency: 1000 })
const sweep = createLFO({ frequency: 0.2, depth: 0.6, type: 'sine' })
sweep.connect(filter, 'frequency')

Waveforms

Type	Shape	Best for
'sine'	Smooth wave	Tremolo, vibrato
'triangle'	Linear ramp	Auto-pan, smooth sweeps
'square'	On/off toggle	Gating, rhythmic effects
'sawtooth'	Rising ramp	Rising sweeps
'sample-and-hold'	Stepped random	Glitchy, robotic effects

const lfo = createLFO({ frequency: 2, depth: 0.5, type: 'square' })

Lifecycle Options

Control how the LFO interacts with sound playback:

// Sync LFO to sound lifecycle — starts/stops with the sound
lfo.connect(synth, 'gain', { syncLifecycle: true })

// Retrigger — reset LFO phase each time the sound plays
lfo.connect(synth, 'gain', { retrigger: true })

Note: syncLifecycle and retrigger are mutually exclusive.

Depth Units

Control how the depth value is interpreted:

// Ratio (default) — depth as fraction of parameter value
lfo.connect(synth, 'gain', { depthUnit: 'ratio', depth: 0.3 })

// Cents — useful for frequency modulation
lfo.connect(synth, 'frequency', { depthUnit: 'cents', depth: 100 })

// Absolute — fixed depth in parameter units
lfo.connect(synth, 'gain', { depthUnit: 'absolute', depth: 0.2 })

Cleanup

lfo.stop()
lfo.disconnect() // Disconnect from all targets
lfo.dispose() // Full cleanup

LFOs connected with syncLifecycle are automatically cleaned up when the target sound is disposed.

Next Steps

• PolySynth -- Add vibrato to a polyphonic synthesizer
• GrainPlayer -- Modulate grain position with an LFO
• API Reference -- Full LFO API docs