Nickname for New York's music district (3,3,5)
I believe the answer is:
tin pan alley
(Other definitions for tin pan alley that I've seen before include "New York City district for popular musicians" , "District concerned with production of popular music - commercial side of pop music" , "Name for the realm of popular music production" , "Realm of popular music producers" , "Commercial side of show business and pop music" .)