DistroLock works best for music that has not yet been distributed. Previously released music may already be in public audio databases, which means it can't be locked by anyone.
The good news: If *you’re* the one who previously distributed it, you already have some protection. That's because responsible stores & distributors may cross-reference their new uploads with public audio databases, and reject unauthorized releases of your music.
Note: Songs with publicly-available audio (generic loops, sounds, and samples) may be rejected by DistroLock. That's because those are sounds everyone is allowed to use - which may trigger positive identifications with other peoples' music.
Hope this helps and thanks for trying DistroLock.