A mystery here.

If you play the first level music "Final Take Off" of After Burner on any home conversion, after the 'rising intro bit' you'll hear a definite tune which isn't present on the Arcade (you only hear guitar chords and a bassline).

Weird thing is, this tune is *exactly the same* on every home conversion: PCE, SMS, Atari ST.
What I can't figure out is where this tune came from!
It always sounded out of place in every home conversion.