Italian tenor standard (1,4,3)
I believe the answer is:
o sole mio
'italian tenor standard' is the definition.
(well-known Neapolitan song written in 1898)
This is all the clue.
(Other definitions for o sole mio that I've seen before include "Italian tune" , "Italian original of Presley's It's Now or Never" , "Neapolitan song" , "Italian song anglicised as It's Now or Never" , "Air" .)