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The Kanto Champion Theme is one I know very well, and of which I am quite fond; it is also one I have heard rearranged Time and again, for Blue, Red, and Lance. This Arrangement is most similar to the Stadium-Style Arrangement used for the final Battle in FireRed and LeafGreen, or else the Rival Battle in the Gym Leader Castle of the original Pokémon Stadium, though it certainly echoes the numerous Generation IV-V Iterations as well. It would be interesting to know which served as the Base.
At the Beginning, it appears the repeated Sequence of four Notes feels a little off. I am not sure whether this was intended, or if I am mistaken, but they do not appear to proceed quite like those in the Original; I think the last Note may be somehow 'higher' than usual, but I know rather little about how Music actually works, so I have some uncertainty saying this.
The Arrangement is otherwise entirely solid, and I enjoyed the Juxtaposition of the Piano and the Electric Guitar especially. The Piano feels rather frantic, which serves to increase the Tension in a Piece of Music that already plays over one of the more intense Scenes of the Game, and raises the Stakes a bit more. The missing Part of the Opening, I did not notice, and I think this is fine without it. Though it is not really bad, the Generation II Arrangement left it out entirely, and I want to say that the only Arrangement of this Theme I think really benefits from it is the Prime Cup Final of Pokémon Stadium, which uses a Flute for it and has a rather unusual Instrumentation, if Memory serves.