LFO Rate Calculator

1Understanding Low Frequency Oscillators

A Low Frequency Oscillator (LFO) generates cyclic waveforms at rates below the audible range—typically 0.01 Hz to 20 Hz. Unlike audio oscillators that produce sound directly, LFOs modulate other parameters, creating movement and evolution in static sounds. Tremolo, vibrato, filter wobbles, and auto-pan effects all stem from LFO modulation.

The "rate" or "speed" of an LFO determines how quickly it cycles through its waveform. A 1 Hz LFO completes one full cycle per second. A 0.5 Hz LFO takes two seconds per cycle. Syncing this rate to musical tempo creates rhythmically coherent modulation that grooves with your track rather than fighting against it.

Our LFO rate calculator converts BPM to Hz for any note division, including straight, dotted, and triplet values. This enables precise tempo-synced modulation even in synthesizers and plugins that only display rate in Hz rather than musical note values.

2Tempo Synchronization Explained

Tempo-synced LFOs create modulation that aligns with musical beats. When a filter wobble cycles exactly every quarter note, it becomes part of the rhythm rather than arbitrary movement. This integration separates professional-sounding productions from amateur ones where modulation seems disconnected from the music.

The mathematics mirror delay time calculation. Quarter note Hz = BPM ÷ 60. At 120 BPM, a quarter note cycles at 2 Hz (120÷60). For other note values, multiply or divide accordingly: eighth notes = 4 Hz, half notes = 1 Hz, whole notes = 0.5 Hz at the same tempo.

Many modern plugins offer note-based sync directly, but hardware synthesizers and vintage plugins often only show Hz. Our calculator bridges this gap, providing exact Hz values for any tempo and note division combination.

3Waveform Shapes and Their Effects

LFO waveform shape dramatically affects modulation character. Sine waves produce smooth, continuous movement—classic vibrato and gentle filter sweeps. Triangle waves are similar but with more linear movement between peaks. Square waves create abrupt jumps between two values—step-sequencer-like effects and trills.

Sawtooth waves rise gradually then drop sharply (or vice versa). These create asymmetric modulation useful for rising filter sweeps that snap back, or vice versa. Sample-and-hold randomly jumps to new values at the LFO rate—the classic "computer" or "random" sound often heard in electronic music.

The rate calculation applies identically regardless of waveform shape. A 2 Hz sine wave and a 2 Hz square wave both complete one cycle per 500ms. Only the shape of that cycle differs, not its timing. Choose waveform for character, rate for rhythm.

4Common Modulation Destinations

Filter cutoff modulation creates the iconic wobble bass sound and evolving pad textures. Tempo-synced filter LFOs make the wobble groove with the beat. Faster rates create aggressive rhythmic pumping; slower rates produce sweeping, evolving textures that breathe with the music.

Pitch modulation at slow rates (below 6-7 Hz) creates vibrato—the subtle pitch wavering that adds life to sustained notes. Faster pitch modulation enters FM territory, creating new harmonic content rather than perceived pitch movement.

Amplitude modulation produces tremolo—cyclic volume changes. This classic effect appears in guitar amplifiers, electric pianos, and synthesizers. When tempo-synced, tremolo creates rhythmic pulsing that integrates with the groove. Our delay time calculator similarly helps sync delay effects to tempo.

Pan modulation moves sound between speakers. Quarter-note pan creates call-and-response between left and right. Faster rates produce disorienting movement; slower rates create gentle stereo drift. Sync ensures the movement relates to musical structure.

5Rhythmic Variations

Straight note values (quarter, eighth, sixteenth) create on-the-beat modulation. These feel locked and predictable—powerful for rhythmic effects but potentially static for evolving textures. Use straight values when you want modulation to emphasize the beat grid.

Dotted notes create the characteristic bounce of many delay effects. A dotted eighth note LFO cycles at 1.5 times the rate of a straight eighth, placing modulation peaks between straight note divisions. This creates forward motion and avoids landing predictably on every beat.

Triplet divisions fit three cycles where two straight notes would go. This creates a swing or shuffle feel in the modulation. Triplet LFOs excel in genres with triplet grooves—soul, R&B, and hip-hop often benefit from triplet-synced modulation.

Combining multiple LFOs at different rates creates complex modulation patterns. A quarter-note LFO combined with a dotted-eighth LFO produces evolving polyrhythmic movement. Calculate rates for both and experiment with how they interact.

6LFOs in Sound Synthesis

In synthesizers, LFOs shape sound over time. A single sustained note becomes interesting when filter cutoff breathes with an LFO. Pulse width modulation via LFO creates the famous PWM pad sounds. Tempo-synced modulation means the sound's evolution locks to your track's tempo.

Modulation depth determines effect intensity. Subtle depth (a few percent) adds life without obvious wobble. Heavy depth (50%+) creates dramatic pumping effects. Experiment with depth alongside rate—fast rates often work better with subtle depth, slow rates can handle more extreme modulation.

Multiple LFOs per voice enable complex modulation. Route LFO 1 to filter cutoff at quarter notes, LFO 2 to resonance at dotted eighths, LFO 3 to oscillator mix at half notes. Each element evolves independently but remains tempo-locked, creating rich, musical movement.

Envelope-controlled LFO rate creates dynamic modulation. LFO starts slow after key press, speeds up as the note sustains. Calculate target rates for different song sections and automate between them, or use envelope-following to make LFO rate respond to performance dynamics.

7LFOs in Mixing Applications

Mix engineers use LFO-based effects for movement and interest. Auto-pan at musical rates creates stereo animation. Tremolo plugins add rhythmic pulsing to static elements. Filter plugins with LFOs turn flat sounds into breathing textures.

Sidechain-style pumping can be approximated with tempo-synced LFO amplitude modulation. Set a quarter-note LFO with sawtooth wave on a pad's volume—it ducks rhythmically like sidechain compression but without needing a trigger source. This technique works well when traditional sidechaining isn't practical.

Chorus and flanger effects use LFOs internally. Understanding their rate in musical terms helps choose appropriate settings. A chorus at quarter-note rate creates different movement than one at 0.3 Hz (free-running). Sync-capable chorus effects benefit directly from calculated rates.

Automation that follows LFO patterns creates mix movement. Instead of static parameter settings, automate EQ frequency or plugin mix at calculated LFO rates. This manual approach offers more control than true LFO modulation while maintaining tempo relationship.

8Advanced LFO Techniques

LFO-to-LFO modulation creates complex patterns. Use one LFO to modulate another's rate—the modulated LFO speeds up and slows down cyclically. Calculate base rates for both LFOs and experiment with modulation depth for organic, evolving patterns impossible with single LFOs.

Quantized LFO output snaps continuous modulation to discrete steps. A quantized filter LFO jumps between specific cutoff frequencies rather than sweeping smoothly. This creates sequencer-like patterns from simple LFO sources.

Phase offset between multiple LFOs creates stereo movement. Two identical LFOs with 180° phase offset produce opposite modulation in left and right channels. Calculate the rate, set identical LFOs on stereo channels, offset phase, and achieve synchronized but opposing movement.

For audio analysis and tempo detection to match your LFO sync, explore our BPM detector tool. When working with hardware requiring Hz-based timing, our latency calculator helps ensure your modulation stays sample-accurate with your DAW.