Itunes is duplicating all music and giving error message

You can have a try Leawo Tunes Cleaner. Just follow below steps. If you still have issues or have a massive music library in iTunes or other music folders that requires a more powerful and less time-consuming option, the third-party software like Leawo Tunes Cleaner can help you. It can not only automatically clean up duplicate songs in iTunes, but also automatically delete duplicate songs in other music folders. If you want to automatically remove duplicates in iTunes, the automatic duplicate remover might have the answer for you.
1. After kicking off Leawo Tunes Cleaner, click the "Clean-up Duplicate" entry. The program provides 2 duplicate scanning modes: Quick Scan mode and Deep Scan mode. Select one of them to scan duplicate songs.
2. You could delete duplicates in iTunes music library by directly clicking "Scan iTunes" button or click "Add" button to load music files for duplicates removing.
3. After loading source music files, click the "Scan" button on the upper-right corner to start scanning duplicates. The program would display all duplicates clearly and suggest what to remove. You could decide which duplicates to delete by checking them and then click the "Remove" button to remove duplicate songs.


For more details, check: How to Delete Duplicate Songs

You need to delete all the music from your ipod, when it tells you to sync music un-tick the box and then click on something else, it will delete all the music from your ipod and then sync the music again. Make sure in your playlists you dont have the same song twice and it is ticked then that means it will be a duplicated song.

Did you move the folder that contains all of your music files? If so, just clear your library and readd the folders from their current location.
If you are trying to sync the iPod with more than one device, it won't find your music and will likely erase the songs on your iPod.