Pietro Aaron (c.1480-c.1550) is the author of five music treatises. The first, Libri tres de institutione harmonica (Bologna, 1516), was composed in Italian and then translated into Latin by the humanist Giovanni Antonio Flaminio (1464-1536); the other four appeared in Italian, which made Aaron a pioneer in this regard. The Thoscanello de la musica, the first of the vernacular treatises, proved very successful and was reissued three times in the course of the sixteenth century under the title Toscanello in musica (Venice, 1529, 1539, 1562). These reissues are very similar to each other, but are clearly distinct from the first edition, in particular by the addition of an appendix (aggiunta) on various questions concerning musica ficta and the modes of Gregorian chant.