There are two unused music clips that can be heard in the NSF file.
The first one is Track 10, an alternate "Game Over" theme with different, plunkier sounding instruments.
The second one is Track 18, which is a "hurry up!" theme for areas such as 1-2, 2-2, etc. where Mario is shown entering the pipe. Obviously, this is unused because you would never have time run down during the cutscene.
You can download the NSF file here.
(Source: Rick L)
(NSF ripped by: Chris Moeller)