GB-Lbl Add. MS 4911, the sole source of an anonymous music treatise, The Art of Music, is among the few manuscripts to have survived the Scottish Reformation. In answer to the puzzle of its authorship, masters of song schools in Edinburgh or Aberdeen have been proposed. A new reading of the text places the date of its creation between 1559 and 1567 and leads to a revised profile of the author, which, as is demonstrated here, the Scottish composer Robert Carvor (1487/8 – c. 1568) uniquely matches. Further supporting Carvor as the author of the treatise is its inclusion of a section of Carvor’s Missa L’homme armé and of a caricature strikingly similar to one found in the Carvor Choirbook (GB-En MS Adv. 5.1.15), where Carvor’s compositions bear his signature. An Appendix includes the first English translation of the rules of faburden, which are unique to The Art of Music (f.94r-f.112r).