Lost all of the music on my classic iPod

Your music should be on the cloud if the music was purchased thru Itunes. If downloaded from CD's you will need the computer that you used to restore the content. In most cases though the ipod classic has outlived your PC so in that case you may not be able to recover it.

I suspect that what may have actually happened is that you allowed a Sync between your iPod and the iTunes programme on the other computer you were using. The symptoms you mention support my theory.

An iPod can only Sync with one iTunes Library. So when iTunes saw the iPod it would have attempted to Sync, but asked you if that was what you wanted to do. It would have warned you that the Sync would erase the current content on the iPod. If you allowed this to occur, then as you were listening to the iPod, the Sync erased it and therefore there was no music left to play.

However, the point tt2 is asking you to check for is whether the iPod itself has failed. If you foloow his kink and it suggests that the iPod is still okay, that reinforces my suggestion that a Sync has erased the content. If that has happened, you can restore that content by Syncing the iPod with the original iTunes Library that you used. If, of course, you still have that computer.

Otherwise, did you back up the music on that previous computer?

See Corrupt iPod Classic - Apple Community. The first section has advice on data recovery from a corrupted device.

tt2