Related Clues:

• Part of a 45
• Less-played 45 part
• Improbable hit
• Less popular song on a single, usually
• Back of a hit single
• Less promising of two songs
• Lesser-played half of a 45
• 45's back
• It's usually not a hit
• Less popular song, often
• Single surface
• Single bonus?
• Surprise hit, maybe
• Hit back?
• Single's opposite