Audio-Rate Modulation

Any parameter can be modulated continuously using modulation words. Instead of a fixed value, these words produce a modulation string that the engine interprets as a moving signal.

All time values are in steps, just like attack, decay, and release. At 120 BPM with speed 1, one step is 0.125 seconds. Writing 4 lfo means a 4-step period.

LFOs

Oscillate a parameter between two values.

saw snd 200 4000 4 lfo lpf .         ( sweep filter over 4 steps )
saw snd 0.3 0.7 2 tlfo pan .         ( triangle pan over 2 steps )

Word	Shape	Output
`lfo`	Sine	`min~max:period`
`tlfo`	Triangle	`min~max:periodt`
`wlfo`	Sawtooth	`min~max:periodw`
`qlfo`	Square	`min~max:periodq`

Stack effect: ( min max period -- str )

Slides

Transition from one value to another over a duration.

saw snd 0 1 0.5 slide gain .         ( fade in over half a step )
saw snd 200 4000 8 sslide lpf .      ( smooth sweep over 8 steps )

Word	Curve	Output
`slide`	Linear	`start>end:dur`
`expslide`	Exponential	`start>end:dure`
`sslide`	Smooth (S-curve)	`start>end:durs`

Stack effect: ( start end dur -- str )

Random

Randomize a parameter within a range, retriggering at a given period.

saw snd 200 4000 2 jit lpf .         ( new random value every 2 steps )
saw snd 200 4000 2 sjit lpf .        ( same but smoothly interpolated )
saw snd 200 4000 1 drunk lpf .       ( random walk, each step )

Word	Behavior	Output
`jit`	Sample & hold	`min?max:period`
`sjit`	Smooth interpolation	`min?max:periods`
`drunk`	Random walk	`min?max:periodd`

Stack effect: ( min max period -- str )

Envelope Modulation

Apply an envelope to any parameter. The env word is the complete form: it sweeps from min to max following a full attack, decay, sustain, release shape. All times are in steps.

saw snd 200 8000 0.01 0.1 0.5 0.3 env lpf .

Stack effect: ( min max attack decay sustain release -- str )

This is the building block. From it, three shorthands drop the parameters you don't need:

Word	Stack	What it does
`env`	`( min max a d s r -- str )`	Full envelope (attack, decay, sustain, release)
`eadr`	`( min max a d r -- str )`	No sustain (sustain = 0)
`ead`	`( min max a d -- str )`	Percussive (sustain = 0, release = 0)

eadsr is an alias for env.

saw snd 200 8000 0.01 0.3 ead lpf .              ( percussive filter pluck )
saw snd 0 5 0.01 0.1 0.3 eadr fm .               ( FM depth with release tail )
saw snd 200 8000 0.01 0.1 0.5 0.3 env lpf .      ( full ADSR on filter )

These work on any parameter — lpf, fm, gain, pan, freq, anything that accepts a value.

Low Pass Gate

The lpg word couples the amplitude envelope with a lowpass filter. Set your amp envelope first with ad or adsr, then lpg mirrors it to lpf.

saw snd 0.01 0.1 ad 200 8000 1 lpg .        ( percussive LPG )
saw snd 0.01 0.1 0.5 0.3 adsr 200 4000 1 lpg .  ( sustained LPG )

Stack effect: ( min max depth -- )

min/max — filter frequency range in Hz
depth — 0 to 1, scales the filter range (1 = full, 0.5 = halfway)

saw snd 0.01 0.5 ad 200 8000 0.3 lpg .      ( subtle LPG, filter barely opens )

lpg reads attack, decay, sustain, and release from the current sound. If none are set, it defaults to a short percussive shape.

Combining

Modulation words return strings, so they compose naturally with the rest of the language. Use them anywhere a parameter value is expected.

saw snd
  200 4000 4 lfo lpf
  0.3 0.7 8 tlfo pan
  0 1 0.01 0.1 ead gain
.

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