Boss Intro is a klaxon that sounds when you enter a boss room. In the game, the sound plays seven times and then the boss battle begins, but the song is actually setup to repeat indefinitely. The recording is setup to mirror the game, with seven chimes, and the looping is set to match.
This title is based on the where the song is heard in the game, the composers should be contacted for an official title.
This song is track 10 in the NSF file.