Before you start searching for your song or aria, it may be helpful for you to recall (or look up):
Then choose one of the following:
Searching in IUCAT
This will work only if the song is published separately.
If you know the name of the opera from which your aria is taken, search for that. (If you don't know the opera, look up the aria in the index at the back of The New Grove Dictionary of Opera ML102 .O6 N5 1992 -- shelved on the Index Table in the Reference section or available at Oxford Music Online.)