John Weeks Moore, Complete Encyclopaedia of Music… (1880)
“ It has been thought that Apollo was the name of the sun, for it may be observed that Apollo's skill in music seems to agree with the nature of the sun, which, being placed in the midst of the planets, makes with them a kind of harmony, and, as it were, a concert ; and because the sun is thus placed, the middlemost of the seven planets, the poets assert that the instrument which Apollo plays on is a harp with seven strings. ”
