Notes of considerable value, we hear, for vocalists (6)
I believe the answer is:
tenors
'for vocalists' is the definition.
(tenor is a kind of vocalist)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for tenors that I've seen before include "Male singing voices" , "Opera singers" , "Male singers from Reston" , "Male singers with high register" .)