Apple Music has messed up my iTunes library
When Apple Music first launched, there was a bug in iTunes version 12.2 that scrambled your iTunes library if you had previously subscribed to iTunes Match. This was subsequently fixed in iTunes 12.2.1, but if you signed up for the free trial of Apple Music before that was released, your library will still be corrupted. If you see the wrong album art, or you click one song and another one plays, then this is why.
Apple offers a solution to this problem at http://apple.co/1JgT6je which requires disabling iCloud Music Library on all your devices as its first step. You then need to update all of your computers to iTunes 12.2.1 to ensure the problem is unable to recur.
Next comes the unfortunate step of resetting your iCloud Music Library from one computer, which has the consequence of removing all of the music and playlists stored in it. You should, of course, ensure you have a local copy of any songs you own that weren’t purchased from the iTunes Store before you proceed to reconstruct the online library. After resetting the online library, you need to restart iTunes in Safe Mode to restore your library (hold down ≈+å when opening iTunes). This has to be done on all of your computers, and afterwards you should check that songs that were previously faulty – in how they were listed or which played wrong items – are now correct, and then turn on iCloud Music Library on all other devices.