Problem: After entering the details of a record and its tracks, I have discovered that there are some tracks with an ID of zero, and no information. Why?
Solution: Not sure why, but I think it has something to do with pre-filling the Artist and Title in the Tracks subform. To clear them, select Queries and open the Delete Null tracks and Tidy Tracks queries. You will be informed that you are going to delete some rows, but that is exactly what you want to do.