Swift library for music theory, currently focused on chords/harmony.

Tonic answers musical questions, such as:

• What's the note for this pitch in this key?

  Note(pitch: Pitch(midiNoteNumber), key: .Bb)

• What's the name of a chord?

  Chord(notes: notes).description

• What chords are in this key?

  Key.Cm.chords

• What chords in this key contain this note?

  Key.C.chords.filter { $0.noteClasses.contains(.C) }

• What notes do these keys have in common?

  Key.C.noteSet.intersection(Key.Cm.noteSet)

• What notes don't these keys have in common?

  Key.C.noteSet.symmetricDifference(Key.Cm.noteSet)

These questions are all tested in our unit tests explicitly.

• Correctness. Try to be as correct with respect to music theory as possible.
• Strong typing. Use types to prevent errors (e.g. Pitch instead of UInt8).
• Good performance. Tonic uses bit sets to represent pitch sets and note sets.

Install using Swift Package Manager.