10 Ways to Use an LFO

Bringing Motion to Your Music

If you’ve ever played around with a synthesizer, be it hardware or software, you will have come across three capital letters emblazoned on its interface: LFO.

And perhaps you’ve wondered: What does this thing do?

Simply put, the LFO introduces motion to your music. It makes a sound change over time.

More accurately, LFO stands for Low-Frequency Oscillator. Like a regular oscillator, the LFO outputs vibrations. But unlike a regular oscillator, it cannot be heard, as it oscillates at a low frequency, typically below 20 Hz, below the range of human hearing.

The LFO waveform’s purpose is to control other parameters on the synthesizer. Think of it as an invisible hand that automatically turns knobs or dials—almost like magic.

Waveforms

Like a regular oscillator, the LFO can generate any of the five classic wave shapes: sine, sawtooth, triangle, square, and pulse.

A sine wave produces smooth, undulating motion, whereas a square wave creates a binary on/off effect. For the examples below, I’m using a triangle wave shape. It’s similar to a sine wave in that it’s symmetrical, but its angles are sharp and formed by straight lines rather than curves.

Modulation Targets

In sound design, we refer to the LFO as a modulation source. The target of this modulation can be virtually any control dial on a synthesizer, such as pitch, volume, pan, filter cutoff, and more.

Below, I’ve outlined ten ways to use an LFO by targeting different parameters. For these examples, I’ve automated the LFO’s frequency to sweep between 0.05 Hz and 30 Hz using a triangle waveform.

The “Classics”

These are the most common uses of an LFO—targets you’ll find on nearly every synthesizer, such as Logic Pro’s RetroSynth or Ableton Live’s Analog.

1. Pitch

Mapping the LFO to the oscillator’s frequency makes the pitch oscillate. Subtle modulation creates vibrato, while deeper modulation sounds like a siren. In this example, you’ll hear the latter.

2. Filter Cutoff

The filter section shapes the brightness or dullness of a sound. Using an LFO to open and close the filter creates a wah-wah effect, reminiscent of a guitar pedal.

3. Pulse-Width

Pulse waves allow for modulation of their duty cycle—the ratio of on/off phases in the waveform. An LFO can change this width dynamically, creating a signature PWM sound.

4. Volume

Modulating volume with an LFO produces tremolo, a classic effect where the sound alternates between loud and soft.

5. Pan

By targeting the stereo position, an LFO can move a sound between the left and right speakers, creating a ping-pong or auto-panning effect. Try listening to this one with headphones.

6. Detune

Many software synthesizers, like Serum, allow you to duplicate an oscillator and slightly detune each copy. Using an LFO to modulate the detune amount makes the sound drift in and out of tune. Similar to vibrato, but not quite.

Effects

An LFO can also modulate parameters within audio effects. For instance, Serum includes an effects section where its LFO can target specific controls.

7. Distortion

Distortion amplifies a signal beyond its limits, clipping the peaks of the waveform. Here, the LFO modulates Serum’s Drive and Mix controls, causing the distortion depth to ebb and flow dynamically.

8. Reverb

Reverb places your sound in a virtual space. Modulating the size of the space with an LFO allows it to expand and contract, creating dramatic and even chaotic effects. In this example, I’ve targeted Serum’s Wet/Dry and Size knobs, producing a sound that evolves from subtle ambience to helicopter-like noise.

Going Meta

An LFO can modulate the rate of another LFO—essentially, modulating the modulation. This technique unlocks even more complex and unpredictable results.

9. LFO → LFO (Rate) → Pitch

Using one LFO to modulate the rate of another that targets pitch produces erratic, glitchy behavior. This technique can add experimental character to otherwise straightforward sounds.

10. LFO → LFO (Rate) → Filter

Here, one LFO controls the rate of another, which in turn modulates multiple filter parameters like cutoff, resonance, and drive. The result is chaotic yet textured—akin to a robot having a heart attack.

Conclusion

These ten examples should not only demystify the LFO and its purpose but also inspire you to experiment with your own creative projects. The LFO offers endless opportunities to bring motion and life to the sounds you’re designing.

Are there any other parameters you’ve targeted using an LFO? Let me know in the comments below—I’d love to hear your ideas!