I remember a perfect selection on a Fresh Aire disk by Mannheim Steamroller. A friendly employee patiently explains the process. She explains that the fee depends on many factors. For my slide show, the master-use fee might be as low as a few hundred dollars. But, she hastens to add, I still need to pay the publisher.
Publishers usually charge the same fee as quoted by the record label.
The subject of sheet music comes up, and I think I see my loophole. American Gramaphone publishes a variety of sheet music, including solo piano. My sister is an accomplished pianist. So, I just make a 1500 mile trip, record her playing my favorite pieces, and synchronize the music with the slides. As you might have guessed, the process isn't that simple.