Even the “DRM Free” ones. They are “unlocked” but in reality, they are connected to you forever by name and other identifying personal information.
Here’s how it works. During the buying process a username and transaction ID are known by the online retailers. Before making the song available for download their software embeds into the file either an account name or a transaction number or both. Once downloaded, the file has squirreled away this personal information in a manner where you can’t easily see it, but if someone knows where to look they can. This information doesn’t affect the audio fidelity, but it does permanently attach to the file data which can be used to trace back to the original purchaser which could be used at a later date.
Retailers aren’t talking, but there’s ample proof of what’s transpiring. Using simple file comparison tools it’s possible to verify this behavior by purchasing identical songs using different accounts and see if they match. I emailed support departments for several retailers asking if they would acknowledge these actions and inquiring about what specific information they are embedding. Only 7digital responded saying they don’t use any watermarks. What retailers won’t say publicly is that the major record labels are requiring this behavior as a precondition to sell their music.
This is a back door to basically impose DRM and user limits on these music files later.