Pitch, harmony, and tuning

Mora treats pitch in separate layers: absolute pitches, coordinates in a scale, chord identity and its voicing, and the tuning that maps degrees to frequency. This page covers each layer, the forms that move between them, and how pitch reaches a MIDI receiver.

notes makes the absolute-pitch intent explicit:

(d1! (>> (notes "f3 ab3 c4 eb4")
         (s "psin")
         (gain 1)))

In Mora’s named-pitch convention, bare C is C3, and C3 is MIDI 48:

notes accepts named and fractional pitches. Fractional numeric pitches remain fractional for capable synthesis targets.

notes is distinct from n, the legacy numeric and sample-index lane, whose interpretation depends on the receiving context. In mini notation, :N after a sound name selects a sample variant, not a pitch. See pattern literals and mini notation.

degrees represents scale coordinates. in-scale maps those coordinates to pitches:

(d1! (>> (degrees "0 0.5 1 1.5 2 2.5 3 3.5")
         (in-scale :minor
                   :root "f3")
         (s "psin")))

Fractional degrees interpolate between adjacent scale degrees. They are not silently rounded.

scale-quantize maps pitches onto a scale. scale-transpose moves in the mapped degree space.

Scale vocabulary can be extended with define-scale:

(define-scale :my-pentatonic '(0 3 5 7 10))

(d1! (>> (degrees "0 1 2 3 4 5 6 7")
         (in-scale :my-pentatonic
                   :root "f3")
         (s "psin")))

Chord identity and its realization as voices are separate. chords describes the chords; voicing realizes them as voices:

(defparameter *changes* (chords "<Fm7 Dbmaj7 Eb7 Cm7>"))

(d1! (>> (voicing *changes*
                  :anchor "c4"
                  :dictionary :closed)
         (s "psin")))

arpeggiate selects actual voices from those chords:

(d1! (>> (voicing *changes*
                  :anchor "c4")
         (arpeggiate "0 ~ 2 [1 3]")
         (s "psin")
         (legato 0.6)))

Arpeggiating chord voices is distinct from choosing sample indices or independently authoring another melody.

define-chord and define-voicing extend the chord and voicing dictionaries.

Mora includes equal-division, ratio-based, and large/small-step tuning descriptions. tune maps degrees to precise frequency. frequency-transpose applies a frequency ratio.

(defparameter *tuning*
  (equal-tuning 31
                :base-frequency 220))

(d1! (>> (degrees "0 6 12 -1")
         (tune *tuning*)
         (s "psin")))

Tuning is independent of temporal meter and independent of the MIDI receiver’s policy. A non-octave period is also representable.

MIDI output requires an explicitly selected and configured receiver. The available policies distinguish strict delivery, quantization, and pitch bend:

• Plain-channel pitch bend is shared by overlapping notes on that channel.
• MPE uses member channels for independent note bends.
• The receiver’s bend sensitivity must match the sender’s declared range.

The individual policies and configuration examples for channel pitch bend and MPE are in MIDI and other outputs.