Regole, passaggi di musica
It contains possible ornaments. Like many of its contemporary sources it uses an example of two notes (an interval) and then shows how you could use an ornament to go from one note to the next. In a type of table-format the book suggests several options for the same interval; by learning those by heart you get a sense for the style and possibilities.
It also explains newer ornaments with their particular names, gives examples of how to apply all of these on top of existing pieces and shows the use of falso bordone, a way to add more voices to an existing line of music.