Route 4's music was the most heavenly theme I had ever heard for a pokemon game. I instantly imagined myself in France upon hearing this theme. Very sophisticated for pokemon music.
Shalour City had a really mystical quality to it. A nice blend of eastern and western instruments.
Upon hearing the music for the Tower of Mastery, I felt like I had arrived at some otherworldly place. It reminded of Celestial Tower, but instead of a place of death, it was a place of life and discovery.
Anistar City was one of the most emotionally moving tracks I've heard in a pokemon game, right up there with N's Farewell. It embodies a sense of sorrow and loneliness that we experience at times. Yet it also sounds very hope filled. It is hard to describe accurately.