Alypius

Alypius was a Greek writer on music theory, author of the surviving Isagoge musica ("Introduction to Music"), a technical manual that tabulates the ancient Greek system of musical notation across its various keys (tonoi). His date is uncertain; he is conventionally placed in late antiquity, roughly the 4th century CE, though earlier datings have been proposed. Almost nothing is known of his life. His treatise is invaluable to modern scholars because its notation tables are the principal key to deciphering the few surviving examples of ancient Greek musical notation.