pub fn parse_key(text: &str) -> Result<KeyReading, MusicError>Expand description
Parses a key name.
A key is major or minor. A mode name such as A dorian is a scale, so
read it through the scale entries.
ยงErrors
MusicError::UnknownKey for text no branch of the grammar accepts,
such as 13A, Z or the chord Am7.