What makes Pokémon awesome are the battles. As you travel on your journey, you may get spotted by a trainer who then challenges you to a battle! The sense of the music is the feeling of competition.
Which trainer battle music do you like best?
I like them all anyway.

Kanto: Red/Blue , Gold/Silver , FireRed/LeafGreen , HeartGold/SoulSilver

Johto: Gold/Silver , HeartGold/SoulSilver

Hoenn: Ruby/Sapphire , OmegaRuby/AlphaSapphire

Sinnoh: Diamond/Pearl

Unova: Black/White , Black/White(Subway) , Black2/White2

Kalos: X/Y