brownian-walker

brownian-walker sends every note you play wandering off on its own.

Lines that drift by chance instead of by scale run all through Xenakis’s Mists; here, each of your notes starts one. Each note-on plants a walker: it sounds the played key immediately at your velocity, then every interval it steps a Gaussian-drawn distance (sigma semitones wide, rounded), sounding wherever it lands. Steps are legato, the note-off of the previous key and the note-on of the next stamped together, so a walker is one continuous voice. The walls at lo and hi reflect: a walker that would step past them folds back into range. Your note-off for the planted key recalls its walker, releasing whatever it is currently sounding. Up to 8 walkers roam at once; a 9th steals the oldest, releasing its current key first.

Note-ons and note-offs are consumed; only the walkers’ voices reach the output, and everything else passes.

The walkers are generators: they run on their own seeded clock, the same seed and the same playing wandering the same paths, and clean up on a scene switch.

Parameters

interval= takes a duration string like "250ms" or "1.5s", or beats= against the tempo, never both; see Time and tempo.

Parameter	Type	Default	Range
seed	integer	required	any unsigned 64-bit value
interval	duration string	"80ms"	at least 20ms
beats	number	none (instead of interval)	finite, greater than 0
sigma	number	2.0	0.5..=12.0 semitones per step
lo	integer	21	key 0..=127, at most hi
hi	integer	108	key 0..=127

Example

miditool.kdl

input "Roland"
output virtual="miditool Out"

brownian-walker seed=29 interval="80ms" sigma=2.0

Hold one key and a line snakes away from it in small chromatic steps, twelve and a half notes a second; release and it stops mid-thought. Hold three keys and three independent lines tangle.

Try this

Slow the stride and widen the steps, penned into two octaves:

tempo 90

brownian-walker seed=4 beats=0.5 sigma=6.0 lo=48 hi=72

Half a beat per step with a wide sigma makes an angular melody that keeps ricocheting off the walls of the range. Then tighten sigma=0.5: the walker mostly stays put, wobbling by semitones, a slow trill that occasionally loses its footing.