If your not familar with midis. It's basicly a computer file that tells a synth engine what instruments do what. While the sound fonts control extra stuff like pitches and, other paremeters normally used in high end engines. I recommened using fl studio on computer. If your on computer use midi clef or, midi voyager so you load the sf (sound font file) otherwise it won't sound right.
The zip can be downloaded from my youtube video in the description going threw adfly. Just heads up. The file is roughly 2gb in size so it's heavy download. But, for those wanting to learn how to play sonic colors music. This shouldn't be a problem .