LFO Rates & Tempo Sync
Below ~20 Hz, a cycling function generator is an LFO. Its rate can be free-running or locked to a musical tempo. In this lesson, we explore how rate shapes the character of modulation, and how syncing to BPM makes that modulation feel rhythmic.
What is an LFO?
LFO stands for Low Frequency Oscillator. "Low frequency" means below the range of human hearing, roughly under 20 Hz. This is the lowest frequency your ear can perceive as a pitch rather than as a rhythm. At these speeds, you don't hear the oscillator as a pitch. Instead, you hear its effect on whatever it's controlling: a wobble in volume (tremolo), a wavering in pitch (vibrato), or a sweep in brightness.
Rate and Feel
At 0.5 Hz, each LFO cycle takes 2 seconds: slow, dreamy movement. At 4 Hz, four cycles per second: classic tremolo. At 8 Hz, the modulation starts to blur. Your ear can barely track individual cycles. Push past 15 Hz and you're at the edge of something new, but we'll save that for the next lesson.
Locking to Tempo
In music, timing isn't measured in Hz; it's measured in beats per minute. If your song is at 120 BPM, a quarter note happens 2 times per second, or 2 Hz. An eighth note is 4 Hz. A sixteenth note is 8 Hz. A dotted note lasts 1.5 times its normal duration. A dotted eighth note equals three sixteenth notes instead of two, giving a lilting, swung feel. A triplet squeezes three notes into the space normally occupied by two, creating a rolling, waltz-like rhythm. Syncing your LFO to the tempo makes the modulation feel rhythmic rather than random.