If an MP3 file is set to the read/only state, rating the song or trying to change the tag properties results in an "Information" dialog that states, "Failed to update the following files:" followed by the filename.
I got this error after copying some MP3's stored on a CD to one of my computers. Files on CD are stored and copied as read/only files.
The part that confuses me is that although the program complains, the changes to the tag appear to stick. Is this information stored elsewhere other than within the file itself?
As a test, I copied one of my read-only files, changed the properties and then did a file compare between the two. To my surprise, the files were the same, but the tag properties were clearly different.
Going one step further, if I then delete the read/only file and then reimport it into the library, its tags return back to the state they were in before I changed them. So it's not a surprise that the file compare didn't show a difference.
I do think that the error message in combination with the fact that the file tag does seem to update can cause confusion. It also gets quite annoying when playing songs that are read/only because at the very end when the play count increments, you get the message that the file failed to update.
It's a tough call and something has to change because while you could change the error to be, "The file "x" is read/only and could not be updated." it doesn't appear to be the case since the tags seem to change. It's only when you remove and then reimport the song is data lost.