Tonic.ts

Tonic.ts is a TypeScript library that provides APIs for music theory, drawing pitch constellation diagrams, and calculating guitar chord fingerings.

Classes

• Note represents musical notes such as "E4" and "F♯5". It converts between string and instance representations.
• PitchClass represents a pitch class: a musical pitch modulo its octave. For example, the pitch class "E" represents "E0", "E1", "E2", etc.
• PitchLike is an interface that includes Note and PitchClass. Chord and Key (below) can be specialized to either a pitch or a pitch class; this interface defines their common type.
• Interval represents a musical interval, such as a minor third or a perfect fifth, between two notes. The difference between two pitch-like instances of the same type is an Interval. A pitch-like instance can be transposed by an interval.
• [[Chord]] is a set of intervals from a root. A chord has a tonic, a a (chord quality), and an inversion. From these can be derived a set of Notes (or pitch classes), and a name. For example, "E Major" and "C Minor" name chords.
• ChordQuality represents the qualities of a chord's component intervals, its suspensions, and additions. The qualities named by "Major", "Minor", and "Dom7" are examples of chord qualities.
• Scale is a named sequence of intervals from an (unspecified) tonic. For example, "Diatonic Major" names a scale.
• Key is a scale that starts at a specific node or pitch class.

Chord and Key are generic classes, that can be instantiated at either Note or PitchClass.

A [[ChordClass]] is to a Chord (and its root) as a Scale is to a Key (and its tonic). The class name hide this symmetry, but they're the names from the domain of music theory.

The API makes use of TypeScript generics. Although it can be used from straight JavaScript, there's better alternatives (link TBD) for that.

Guitar Chord Calculator

frettingFor and allFrettings find guitar chords (or chords on other polyphonic fretted stringed instruments) for a chord.

Chords are filtered and sorted according to voicing and play-ability metrics: number of open strings, distance between closed frets, presence of barres.

Graphics Module

The diagram module contains functions to render chord diagrams and pitch constellations.

These functions haven’t been tested since this package was ported from CoffeeScript.

License

MIT