Anything from this soundtrack. It's got a LOT of stuff, including a few medleys in its own run.
Mind you, the music from this game portrays the feel of the environment and the events occurring pretty well. It would not be farfetched to perform the entire soundtrack as one long concert opera; more to the point, it may be disconnected to just play, for example, Seaside Town or Midas River on its own.
Hour-and-a-half long playing sessions aside, a small medley "describing" a part of the game (an event sequence) in a similar way to how it naturally is musically in-game would be interesting. For example, rose town/geno awakens/beware the forest's mushrooms/fight against an armed boss/get a star. Or something around Nimbus/Barrel Volcano/Axem Rangers, though this would be longer because of the huge sequence of events that takes place there (Nimbus town, the castle, Dodo, battle with Margerie Margeritta, Barrel Volcano, Axem Rangers...).
The most obvious, of course, would be to start at Goodbye Geno and play the entire ending sequence.
