As a new user, I was puzzled when I opened a single MP3 file and changed some metadata settings, but could not figure out how to save them. I didn't realized that I had to select the file. With a single file loaded, I assumed that it was selected by default. I did not understand that I can select a whole folder and change settings for selected multiple files, which is a great feature.
I suggest that the software should warn the user if they change settings but no files are selected -- especially if they then try to exit the program. This may be redundant or unnecessary for experienced users, so I also suggest that this be a settable preference so experienced users can turn it off if they do not need it.
IMHO, the program should never allow a user to exit with unsaved changes.