The cause of this problem is incorrect information in the FreeDB database. For example, it may contain "Concerto in A / something" in the track title, and according to FreeDB specification, this translates to:

Artist = Concerto in A
Title = something

Which is wrong, of course. To correct this problem:

- Open album properties, switch to the Tracks page.

- Click More button and make sure there is a checkmark next to the "Show Artist" menu item. That way, the track list consists of 4 columns: number, title, artist and time.

- Apparently, there are some incorrect artists in the list, since the album created another folder. Correct the artists by selecting tracks, typing the correct artist name (e.g. Bach) and pressing Enter.

- Press OK to save all the changes you made.

- Individual track artists are now correct, so the additional folders will disappear.