"And Apollo, let us remember, was the god of music.

Apollon is Thrice-Great Hermes or Hermes Trismegistus¡"

What?
Apollo was a solar deity adopted into the Greek pantheon from either the Hittites or possibly from Hyperborea , that is, Northern Europe.
He became the God of Music, Archery and Shepherding. Son of Leto and Zeus, he had a twin sister, Artemis.
Hermes was probably adopted from India. Originally a god of twilight of the wind, became patron god of thieves after stealing Apollo's cattle, was also the god of travel and as Hermes psychopompos, the conveyer of souls to the underworld. The title Trismegistos comes from a connection and an identification of Hermes with the Egyptian god, Thoth.
Thoth was said to be the inventor of all the Arts and Sciences as well as writing. He was thought to be all powerful, and it was this Egyptian concept that was translated into Greek as Trismegistos. Thoth was a moon god!
The Celtic Dagda was also identified with Hermes/Mercury by the Romans.
(from Larousse Encyclopedia of Mythology and the Oxford Classical Dictionary).

Three very different and separate characters!
Music theory is fascinating, and so is mythology, but to be any use, theory, mythology and maths need to be accurate.
Cheers
Dave