Possible Clues:

• It takes two
• "Say, Say, Say," say
• Performing pair
• Song such as Lady Gaga and Bruno Mars' "Die With a Smile"
• Daft Punk, for one
• Tune two croon
• Song such as "Shallow"
• Operatic piece
• Sonny & Cher hit
• Song such as "Islands in the Stream"