Musical master (8)
I believe the answer is:
virtuoso
'musical master' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for virtuoso that I've seen before include "Person who excels in techniques of singing or playing music" , "Great musical performer" , "Brilliant -- prodigy" , "Great player" , "Highly-skilled performer" .)