40 sheets heard by singers (5)
I believe the answer is:
choir
'singers' is the definition.
(group of singers)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for choir that I've seen before include "warblers" , "Chorus in church" , "set of singers" , "They sing" , "Group of singers, often in church" .)