Riku's heart began to beat faster even with just the tuning of the violin. There was just something so wonderful about listening to the Prince play. And this was just for him. Solely and completely for him. Riku loved it. (Alright, the ladies next door could probably hear faint strains of music, and the guards outside their door, but it was FOR Riku)
With the pulse of the music, Riku's heart raced faster so by the time the Prince took a lull in the song, Riku was quite out of breath, kind of puddled on the bed, watching the Prince with hazy eyes and breathing hard.