type Subdivision = "1m" | "1n" | "1n." | "2n" | "2n." | "2t" | "4n" | "4n." | "4t" | "8n" | "8n." | "8t" | "16n" | "16n." | "16t" | "32n" | "32n." | "32t" | "64n" | "64n." | "64t" | "128n" | "128n." | "128t" | "256n" | "256n." | "256t" | "0"

Represents a subdivision of a measure. The number represents the subdivision. "t" represents a triplet. A "." add a half. e.g. "4n" is a quarter note, "4t" is a quarter note triplet, and "4n." is a dotted quarter note.