Butterflies' melancholy music (5)
I believe the answer is:
blues
I believe this is a triple definition!
'butterflies'' is the first definition.
(blue is a kind of butterfly)
'melancholy' is the second definition.
(I've seen this before)
'music' is the third definition.
(blues is a kind of music)
(Other definitions for blues that I've seen before include "Depression - music" , "Feeling of sadness or depression" , "Lady Sings the - - (film)" , "State of depression" , "Oxbridge athletes" .)