Theory and Microtonality

Scale-relative writing keeps a motif’s relationships intact when you change its key. Microtonal writing uses the same model with intervals between the usual semitones.

A scale is an interval set and a key has a root

A Scale describes ordered intervals without an absolute root. A Key places that scale at a note. Degree 1 is the root, and higher degrees walk through the scale rather than adding chromatic semitones. Thus a fifth-degree motif can retain its role when its key changes.

let major = Key(C4, "major");
let minor = Key(C4, "minor");
print(major.degree(3));
print(minor.degree(3));

A track key resolves degree events and quantizes absolute notes onto its scale. This is a musical choice: an out-of-scale note may move when the track has a key. Use absolute pitches without that quantization when their precise chromatic placement is intended.

Diatonic chords choose notes from the key. An explicit chord quality chooses its interval recipe, so a quality such as min7 and a diatonic seventh chord are different requests.

Fractional semitones retain pitch detail

Custom scales can contain fractional semitones. Their repeat period defaults to the twelve-semitone octave; a custom period changes where the interval set repeats. A Scala tuning supplies an interval set from a file. These choices describe pitch relationships without requiring twelve equal steps.

An instrument still determines how that pitch is realized. MIDI note numbers identify semitones, so microtonal output uses pitch bend around a nearby MIDI note. With ordinary channel-wide bend, overlapping notes share the bend and can affect one another. MPE gives each note a member channel so its pitch bend can be independent. The receiving synth’s mode and bend range must match.

Write in a Key and Play Microtonal and MPE show the actions. Theory specifies the values and methods.