@spec chord(term(), atom() | String.t(), keyword()) :: [integer()]

The notes of a chord, as MIDI numbers.

:num_octaves repeats it up the keyboard; :invert moves the lowest notes up an octave that many times.

@spec chord_degree(integer(), term(), atom(), pos_integer(), keyword()) :: [integer()]

A chord built on the degreeth note of a scale: count notes, every other scale step.

:invert as chord/3.

@spec chords() :: [atom()]

The chord names known.

@spec degree(integer(), term(), atom()) :: integer()

The degreeth note of a scale as a MIDI number, counting from 1.

@spec hz(term()) :: float()

The frequency of note in hertz. A float is already one.

@spec hz_to_midi(number()) :: float()

A MIDI number, fractional, for a frequency in hertz.

@spec midi(term()) :: number() | nil

The MIDI number of note, or nil for nil. Hertz become a fractional number.

@spec midi(term(), keyword()) :: number() | nil

midi/1, moved to octave octave when one is given.

@spec midi_to_hz(number()) :: float()

Hertz for a MIDI number, which may be fractional.

@spec name(number()) :: atom()

The name of a MIDI number, the way TuningFork.Notes.name_of/1 spells it.

@spec scale(term(), atom() | String.t(), keyword()) :: [integer()]

The notes of a scale as MIDI numbers, from root up :num_octaves octaves (default 1) and the note above.

@spec scales() :: [atom()]

The scale names known.