Thomas Ravenscroft is best-known as a composer of rounds owing to his three published collections: Pammelia and Deuteromelia (both 1609), and Melismata (1611), in addition to his harmonizations of the Whole Booke of Psalmes (1621) and his original sacred works. A theorist as well as a composer and editor, Ravenscroft wrote two treatises on music theory: the well-known A Briefe Discourse (1614), and 'A Treatise of Practicall Musicke' (c.1607), which remains in manuscript. This is the first book to bring together both theoretical works by this important Jacobean musician and to provide critical studies and transcriptions of these treatises. A Briefe Discourse furthermore introduces an anthology of music by Ravenscroft, John Bennet, and Ravenscroft's mentor, Edward Pearce, illustrating some of the precepts in the treatise. The critical discussion provided by Duffin will help explain Ravenscroft's complicated consideration of mensuration, in particular.