Everything that the apple tv is able to do, the iPad can do it. Is it an apple tv 1 and you have files stored on it? I have the apple tv 2, and a PC with iTunes running as a media server, using home sharing. So all my medias are on the PC, and I can watch movies or listen to music from any iOS devices as I see fit.
I guess that your music collection is on the apple tv 1.. The only solutions would be to copy your music on your iPad. If your are using live Internet radios, shout cast is available on the iPad, giving you the same choices as the apple tv.
VicoPad addict!