Strabo Geography 10.3.10

[10] And on this account Plato, and even before his time the Pythagoreians, called philosophy music; ¹ and they say that the universe is constituted in accordance with harmony, ² assuming that every form of music is the work of the gods. And in this sense, also, the Muses are goddesses, and Apollo is leader of the Muses, and poetry as a whole is laudatory of the gods. And by the same course of reasoning they also attribute to music the upbuilding of morals, believing that everything which tends to correct the mind is close to the gods. Now most of the Greeks assigned to Dionysus, Apollo, Hecate, the Muses, and above all to Demeter, everything of an orgiastic or Bacchic or choral nature, as well as the mystic element in initiations; and they give the name “Iacchus” not only to Dionysus but also to the leader-in-chief of the mysteries, who is the genius of Demeter. And branch-bearing, choral dancing, and initiations are common elements in the worship of these gods. As for the Muses and Apollo, the Muses preside over the choruses, whereas Apollo presides both over these and the rites of divination. But all educated men, and especially the musicians, are ministers of the Muses; and both these and those who have to do with divination are ministers of Apollo; and the initiated and torch-bearers and hierophants, of Demeter; and the Sileni and Satyri and Bacchae, and also the Lenae and Thyiae and Mimallones and Naïdes and Nymphae and the beings called Tityri, of Dionysus.

[10] Hence Plato, and, before his time, the Pythagoreans, called music philosophy. They maintained that the world subsisted by harmony, and considered every kind of music to be the work of the gods. It is thus that the muses are regarded as deities, and Apollo has the name of President of the Muses, and all poetry divine, as being conversant about the praises of the gods. Thus also they ascribe to music the formation of manners, as everything which refines the mind approximates to the power of the gods.

The greater part of the Greeks attribute to Bacchus, Apollo, Hecate, the Muses, and Ceres, everything connected with orgies and Bacchanalian rites, dances, and the mysteries attended upon initiation. They call also Bacchus, Dionysus, and the chief Daemon of the mysteries of Ceres. ¹ The carrying about of branches of trees, dances, and initiations are common to the worship of these gods. But with respect to Apollo and the Muses, the latter preside over choirs of singers and dancers; the former presides both over these and divination. All persons instructed in science, and particularly those who have cultivated music, are ministers of the Muses; these and also all who are engaged in divination are ministers of Apollo. Those of Ceres, are the Mystae, torch-bearers and Hierophants; of Dionysus, Seileni, Satyri, Tityri, Bacchae Lenae, Thyiae, Mimallones, Naïdes, and Nymphae, as they are called.