1. It is agreed that all sound which is the material of music is of
three sorts. First is _harmonica_, which consists of vocal music;
second is _organica_, which is formed from the breath; third is
_rhythmica_, which receives its numbers from the beat of the fingers.
2. For sound is produced either by the voice, coming through the
throat; or by the breath, coming through the trumpet or tibia, for
example; or by touch, as in the case of the cithara or anything else
that gives a tuneful sound on being struck.