Jun Senoue on Sonic Heroes Vocal Trax:

Unknown from M.E. …Theme of “Knuckles”

I think there would also be many people who know that the lyrics of the characters’ theme songs of Sonic Adventure and of those of Sonic Adventure 2 are almost the same. It’s the extent of minor change suitable for the song’s length even if there’s any because I didn’t want to change it beyond making such things like the inside of character as the theme. This song was impressive since during the demo, which Tokoi finished all by himself, including the song and rap.

[Source]