Having variations in tune quality (7)
I believe the answer is:
unequal
'having variations' is the definition.
(unequal means with variation or differences)
'in tune quality' is the wordplay.
'in' indicates a hidden word.
'UNEQUAL' can be found hidden inside 'tune quality'.
(Other definitions for unequal that I've seen before include "Asymmetrical" , "Not well matched or even" , "Not uniform" , "Not fair or balanced" , "Not evenly balanced" .)