Cloud, I will vouch and say I am the resident 508 expert.
The way I deem something like that passes 508 is that the station should not automatically start on page load. Also all controls must be operable using the keyboard. In other words, I can hit play/pause, stop, forward, back by tabbing to it and hit the space/enter key to activate it. The volume should also be able to be adjusted using the keyboard, I would say once it is given focus, the arrow keys should adjust it.