Accidentally renamed entire music library (25000 songs) - how to revert and have correct artist / album names

Just added a new CD to my Music app (Mac). When it was downloaded, there was no artist or album info. I tried to add artist and album name by selecting all songs under 'get info', and added the band name and album. Unfortunately, I didn't realize I had selected every single album in my library, and renamed them as well. Also, conveniently, my Time Capsule recently stopped working, so I don't have easy access to a hard backup for this. Any suggestions on how to fix this?