Sorry Mike, I didn't understand. Each song in the library has a unique title, otherwise MS will ask to overwrite it.
Please, could you explain what you mean?
MobileSheets allows songs to have duplicate titles. Files used in the library have to have unique file names unless you manage your own files and folders. That error message is only displayed when MobileSheets encounters a situation where it's trying to a find a matching song between two different libraries, yet it encounters multiple songs that have the same title and filenames, and the database IDs are different so it can't figure out which is the right match. This can happen if you use the "Copy Song" feature but don't rename the song to have a unique title, for example.