Google Play Music received a “how-the-hell-did-they-not-think-of-this-before” update giving users the ability to recover cloud-deleted music for up to 28 days. Recovering deleted music is as simple as selecting the “gear” icon in the upper right hand corner while in the web Google Music player and selecting “Music Trash” from the options. From there, you can permanently delete or undelete music in your trash can.
Keep in mind that once permanently deleted, music purchased from the Google Play Store will have to paid for all over again, should you later reconsider. Just avoid unless completely necessary. For example, if a drunken night out yielded an impromptu download of Kesha (above) — perm delete with extreme prejudice. In fact, might want to purge your entire music collection just to be safe, lest you catch a disease.