ThunderPX, on 17 July 2012 - 09:33 AM, said:
What's the deal with some songs being completely different between the GG and SMS versions, anyway? There's also the boss music in Sonic 2, and maybe others (I haven't played any of the 8-bit Sonics in years so I dunno.)
The explanation comes from the SMS having a mono audio output, while the GG have a stereo audio output. When the SMS games were ported to the GG, they ended up rearranging the songs, with stereo support this time. Because of this, some songs ended up sounding different from their SMS counterparts (Turquoise Hill and Aqua Planet, for example), while other songs were completely substituted by other songs made from scratch (Gigalopolis is one of them).
Sonic Blast is a different case, however. When Tectoy ported Sonic Blast for the Master System, it was the other way around, though they kept the songs exactly like the original, albeit the lack of stereo panning.
I grew up with the Sega Master System version of the 8-bit games, so I personally think that all of the Game Gear music rearrangements sucks.