Thankfully, i Tunes makes this seemingly tedious chore a simple one.
In i Tunes, make sure the Menu bar is showing (click the dropdown box in the upper-left corner for that option), and go to View Show Duplicate Items.
So, with your files downloaded from One Drive to your Downloads folder, open i Tunes and go to File Add to Library to move the files to i Tunes.
One of the options will be Download or Download Album.
People frequently stash things there, often in a disorganized fashion, and then quickly forget about them.
Unlike an attic, which has become a de facto graveyard for many CD collections, the cloud is a useful tool for music fans.
To avoid such an occurrence, click the Same Album button centered at the top of the list.
Now the list will show you duplicates that are only on the same album.