Italian theorist and musician. Born in Florence, he was cantor at the Imola cathedral from about 1515 through 1522. From 1525 maestro da casa to the Grand Prior in Venice of the Order of St John of Jerusalem; he entered the monastery of S. Leonardo in Bergamo in 1536.
Aaron's writings, which were attacked by Gaffurius and defended by Spataro, include an important discussion of the application of the theory of modes to polyphonic compositions; other topics include counterpoint and cadence formation in four voices.