So I have two theories as to the evolutionary telos of the human capacity to comprehend and enjoy music.
The first theory is that it was, originally, functional as a way of exciting ancient tribalists for war. Music is a great way of alleviating negative energies within the organism. The primal bass of the drum, chanting, etc can provide an evolutionary advantage to those tribes that use it before heated combat engagements; the warriors will be more brave and energized.
The second theory is that music acts as a form of will to power via internal clarity; music for most people is something that they can relate to on a very personal, deep level. The music that an individual takes kindly to is that which most resonates with his or her inner most essence. The music acts as an articulation device; bringing internal clarity to the organism - reminding it of itself, i.e., its desires, profound memories, and hopes hence the common phenomena of " the chills " ( I.e., hair standing up on arms - euphoric electric sensation that runs throughout the body). That electrical chill is the experience of power; power via self-knowledge, self-articulation. " Knowledge is power" - Francis Bacon. This can provide an evolutionary advantage to the organism as it keeps it motivated to continue in the fight for existence. And not to mention the side benefits of stress relief and increased creativity.
