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miditool

wedge-mirror

wedge-mirror reflects notes around an axis key: what you play above it sounds below, and the other way around.

The mapping is out = 2 * axis - key, the contrary-motion wedge of a Bartok mirror or an inversion canon. A rising line falls, a falling line rises, and the axis key maps to itself. With probability below 1 each note tosses a seeded coin and only that share of them mirrors, so your line frays into two voices leaning away from each other.

The same seed gives the same coin tosses forever; see Seeds. Each note-off lands on whichever side its note-on chose, so held notes always release correctly. A reflection that leaves the MIDI range drops the note, and its note-off with it.

Parameters

Section titled “Parameters”
Parameter Type Default Range
axis key number 60 (C4) 0..=127
probability number 1.0 0..=1
seed integer 0 any unsigned 64-bit value; only matters below probability=1

Example

Section titled “Example”
miditool.kdl
input "Roland"
output virtual="miditool Out"


// A mirror canon in one line. Around D, the white keys map onto
// themselves, so diatonic playing answers itself in the key.
fork {
    pass
    wedge-mirror axis=62
}

Try this

Section titled “Try this”

Mirror only half your notes:

wedge-mirror axis=66 probability=0.5 seed=7

Or keep the original and add its inversion, an instant mirror canon in rhythmic unison:

fork {
    pass
    wedge-mirror axis=60
}

The fork merge plays both voices; the axis note itself comes through once, not doubled.