This is a cute little object that appears if you are lucky enough to find one of the warp whistles hidden in the early levels of the game. Upon activating the whistle, you hear the first measure of this object, a little melody that seems have a b minor feel, (though there are a couple other ideas around that). Then you are transported to the warp map, where these four measures are repeated over and over until you select the world you want to warp too.
One interesting melodic tidbit to pay attention to is the turn around at the loop. Notice the chromatic decent from Bb to G. This is the same melodic profile of the flute melody (D chromatic down to B, four descending semitones). It is a nice musical relation between these objects which are obviously related in game play.
Its nice a simple, alternating between C and Db Major chords, with C as the obvious central harmony. This is due mainly because at the loop repeat the melody descends chromatically to, emphasizing the prevalence of that harmony (C major).
Fans of a bit of reduction or prolongational theory might be interested to see that this is just one big C major chord that happens to be embellished by a chromatic upper neighbor: