1. There are three parts of music, namely, _harmonica_, _rhythmica_,
_metrica_. _Harmonica_ is that which distinguishes in sounds the
high and the low. _Rhythmica_ is that which inquires concerning the
succession of words as to whether the sound fits them well or ill.
2. _Metrica_ is that which learns by approved method the measure of
the different metres, as for example, the heroic, iambic, elegiac,
and so on.