While I sequenced this, it was all done from W3sp's arrangement for piano. All credit really goes to him. It differs a bit from the original, but he's done an amazing job. Again, this is just a MIDI of W3sp's rendition. Download his sheet music and hear his MP3 at:
http://www.gamemusicthemes.com
It's under the SEGA Game Gear section.

By the way, Yuzo Koshiro is the composer for such legendary games as Sonic the Hedgehog, Actraiser (my favorite), Shenmue and more. Check him out.