Musician's original duet played with softened tone (5)
I believe the answer is:
muted
'with softened tone' is the definition.
(eg with muted colours)
'musician's original duet played' is the wordplay.
'original' indicates taking the first letters.
'played' indicates an anagram.
The first letter of 'musicians' is 'm'.
'duet' anagrammed gives 'uted'.
'm'+'uted'='MUTED'
(Other definitions for muted that I've seen before include "(Of sound/colour) softened" , "Quietened" , "Hushed or stifled" , "Not loud" , "Piano" .)