resonance-halo

resonance-halo makes the sustain pedal mean something before the piano: while it is down, every note excites a quiet halo of its neighbors.

The model is the held-pedal haze of Ligeti’s piano writing, where the pedal turns single strikes into a standing wash of adjacent resonance. The effect tracks the pedal itself (CC64 per channel, a value of 64 or higher is down; the pedal message passes through to your DAW as usual). It only deposits while the pedal is down: each note-on then passes unchanged and deposits the width nearest keys on each side (the nearest sieve members when sieve= is given; the played key is never its own neighbor), each sounding at level times the note’s velocity and fading out after decay. Lifting the pedal does nothing retroactive: deposited halos decay on their own schedule. With the pedal up the effect is a pure pass.

The played note releases when you release it, and every halo note is deposited together with its own scheduled note-off, so note-ons and note-offs always balance and nothing hangs. The halo is deterministic, no seed.

Parameters

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

Parameter	Type	Default	Range
width	integer	3	1..=6 neighbors per side
level	number	0.25	0..=1 fraction of the note’s velocity
decay	duration string	"3s"	positive, "250ms" or "1.5s" form
beats	number	none (instead of decay)	finite, greater than 0
sieve	string	none	non-empty sieve expression

Example

miditool.kdl

input "Roland"
output virtual="miditool Out"

resonance-halo width=2 level=0.2 decay="2s"

Play with the pedal up and nothing changes; press it and every note arrives inside a two-second shimmer of its four nearest keys.

Try this

Tune the resonance. Confined to a pentatonic sieve, the halo rings like sympathetic strings tuned to a scale:

resonance-halo width=3 level=0.3 decay="4s" sieve="12@0|12@2|12@4|12@7|12@9"

Whatever you play, its haze is C pentatonic. Then put it after cluster-fist, as the cowell scene of examples/clouds.kdl does, and every fistful rings inside its own halo.