LFOs

LFO stands for low-frequency oscillator. In music technology, an LFO is a modulation source that generates periodic waveforms at sub-audio frequencies, typically below 20 Hz, though some devices expose higher rates. It is used to modulate parameters rather than produce audible tones on its own.

Common waveforms include sine, triangle, square, and sawtooth, with some units offering random or sample-and-hold. LFOs can also be multiform, offering multiple outputs or phase control. The amount of modulation is described as depth; the speed as rate; both can be controlled manually or by a tempo clock in synchronized setups.

Typical applications include tremolo (amplitude modulation), vibrato (pitch modulation), and modulating filter cutoff or resonance to create movement in timbre. LFOs may also modulate panning or oscillator PWM to create spatial or timbral effects. Some LFOs offer bipolar vs unipolar outputs, affecting whether modulation swings around a center value or not.

LFOs can be free-running or tempo-synced to a host or clock. In sequenced or tempo-based systems, LFOs can retrigger on beat positions or stay continuous. In modular environments, multiple LFOs and destinations can be cross-modulated for complex effects.

Origin and use: LFOs date to early analog synthesizers and remain a fundamental tool in subtractive synthesis, FM, wavetable, and digital modular setups for adding movement to patches without introducing new audible content by themselves.