What are some philosophical stances on art and its purpose? I know this is a broad question, but any sources or thoughts would be great.
I am particularly interested in music.
Adorno might be interesting to you, but consider looking at certain composers who also “write” — Cage and Xenakis come to mind.
Attali’s Noise: The Political Economy of Music is also highly recommended in this vein.
I came up with a list of things that good music communicates. I'll repeat it here:
Emotion (or drama)
Imitation (of nature)
Bigness (or awe)
Virtuosity (of the performer)
Practical social functions (like dance or work songs)
Unifying social functions (like anthems)
Memory (or recognition)