It is what anything hangs on.
[115] This is an apostrophe to the nine spheres (_see former note_), which were believed by the ancients to send forth in their revolutions a grand harmony, too loud for mortals to hear.

But no music of the lower region can make up full harmony without the bass of heaven's organ.

The _music of the spheres_ was to Milton the embodiment of the theory of the universe.

He uses the symbol often.
[116] _Consort_ is the right word scientifically.

It means the _fitting together_ of sounds according to their nature.