How loud the note is. Like so many things, assumes from the previous note. As you might expect, this tells the muller what instrument this should be played on. It standardly assumes the instrument of the previous note. Currently, it's up to the muller to guess, becaus ewe haven't gotten into style sheets at all.
Ideas are welcome.
These are performace notes as if to a person reading the score. The muller will generally make no attempt to comply with these directives, just pass them on. The content of the NOTE element is the word or syllable to be sung on that note.