Hélie Salomon’s Scientia artis musice (1274), is a practical manual devoted to basic concepts, psalmody, vocal pedagogy, the musical hand in singing, clefs as indicators of the tone (mode) to which a piece belongs, and practical instruction in the singing of four-voice parallel organum. Joseph Dyer presents the first, much-needed, modern edition of Salomon’s treatise, accompanied by a full English translation, comprehensive introduction and commentary. This edition corrects errors in the 1784 edition of Martin Gerbert, includes the music of chants omitted by Gerbert from the tonary, and makes available reproductions in colour of the eight illustrations in the treatise.