Complex sentence: The elements of music that comprise expression include dynamic indications, forte or piano, phrasing, differing qualities of timbre and articulation, color, intensity, energy and excitement all at the service of the composer's intention as best perceived by the performer.
Split into simpler sentences: The elements of music that comprise expression include dynamic indications, such as forte or piano, phrasing, differing qualities of timbre and articulation, color, intensity, energy and excitement. All of these devices are at the service of the composer's intention and they can best be interpreted by the performer.