Like a lot of my other themes, I had this in my head for a while, wasn't easy putting all those notes in the right place. I wanted the bamboo flute for his theme, but the one plugin I got that has it was a demo, thus was unavailable for use. x( The flute I used however does sounds somewhat similar, so it's not so bad. The flute and drum have that Japanese feel to them, since Spirit was brought up in his training much like a samurai, the bell used more or less represents the "twinkling" of stars at night, and Spirit is a Moon Child, thus has a few "star" moves. The guitar is implemented as a way of representing that while the flute somewhat represents Spirit's calm and pacifistic demeanor, the guitar represents his seriousness in a fight, so the flute and guitar together represent his "calm aggression".
Overall, theme represents Spirit being somewhat of an old-fashioned character in a futuristic setting, even though he is born in that era. Hence the mix of traditional Japanese music plus the more modern feel the guitar brings.