Book excerpt: Early Music History is devoted to the study of music from the early Middle Ages to the end of the seventeenth century and includes manuscript studies, textual criticism, iconography, studies of the relationship between words and music, and the relationship between music and society. Articles in volume 21 include: Aaron's interpretation of Isidore and an illustrated copy of the Toscanello; Musica mundana, Aristotelian natural philosophy and ptolemaic astronomy; The Triodia Sacra as a key source for late-Renaissance music in southern Germany; The debate over song in the Accademia Fiorentina.