Sonny and Cher maybe producing quiet tune (4)
I believe the answer is:
pair
'sonny and cher maybe' is the definition.
(Sonny and Cher were a musical duo)
'quiet tune' is the wordplay.
'quiet' becomes 'p' (music symbol for 'piano', ie soft or quiet).
'tune' becomes 'air' (air can mean a piece of music).
'p'+'air'='PAIR'
'producing' acts as a link.
(Other definitions for pair that I've seen before include "Put together - two of a kind" , "Husband and wife" , "E.g. two aces; mate" , "Set of two" , "Two of a kind, as in cards" .)