tremolo

Periodic amplitude modulation. A low-frequency sine wave is multiplied into the signal, making the loudness pulse over time. Often used to add “life” to a sustained tone — a steady ring becomes a slowly breathing ring.

Compare with vibrato (which would modulate pitch, not amplitude — a different operation that isn’t currently in the DSL).

Signature

signal.tremolo(rate_hz, depth) -> Signal

• rate_hz — modulation frequency. Musically useful range is 3–8 Hz. Below 1 Hz feels like volume swelling; above ~15 Hz starts to sound like AM synthesis rather than tremolo.
• depth — 0 to 1. 0 is no modulation; 1 swings the amplitude between 0 and the input’s full level (100 % tremolo). Subtle musical settings sit around 0.3–0.5.

The LFO starts at full amplitude (cos(0) = 1) so the signal’s onset is not attenuated. The phase reaches the minimum after half a period.

Example

// A 1700 Hz ring with a gentle 4 Hz tremolo wobble.
patch("ping", "one_shot",
    sine(1700.0, 2.5)
        .env(0.008, 1.2)
        .tremolo(4.0, 0.3)
        .fade_out(0.4));

// Heavy tremolo as a "stuttering" effect.
patch("stutter", "one_shot",
    sine(220.0, 1.0).tremolo(10.0, 0.95));

Composing with env

env shapes the body decay; tremolo lays a wobble on top. They multiply, so the order doesn’t matter mathematically — .env(...).tremolo(...) and .tremolo(...).env(...) produce identical output. Read it whichever way scans better.

Notes

• Tremolo on filtered noise modulates the whole noise band, not the bandpass centre frequency. The result is the entire shaped spectrum pulsing in volume. For a “pitch-wobble” effect on filtered noise you’d need a time-varying filter, which isn’t in the DSL yet.
• Stacking tremolo and fade_out is fine. Tremolo modulates ongoing amplitude; fade_out catches whatever’s left at the end. The combination produces a wobbling tone that decays cleanly to silence.
• depth above 1 clamps to 1. No hard limit on rate_hz but rates above the Nyquist limit will alias.