I was going to start this post with the word "music," but stopped when I realize that the word has been corrupted so that I can no longer trust that what I mean will have any relation to what the word connotes in modern usage. I learned this from attempting a search on "music." I was looking for scores; what came up were CDs and downloads.
Honesty compels me to reveal that my own definition of music had to undergo quite an evolution.
When a young child music meant certain specific sounds: My Cuban mother singing Cielito Lindo; a live string quartet playing right in front of me on a pre-dawn Christmas morning; the singing of the choir I joined at six; the magical sound of Mrs. Swenson's piano.
Sure that every musician shared such a specific sense of what it is, I looked forward to studying music in a conservatory. My disappointment began as I heard student after student playing like windup toys, and continued to grow as I sat through interminable hours of required Music Theory, learning rules that had nothing to do with the way my ear worked. I learned more about music as a Liberal Arts student hanging out with kids who loved literature so much that they read it aloud after dinner.
The essence of music is contained in the setting of the word by Henry Purcell (Music for a While): Both syllables sung on a single pitch, G; then repeated a fifth higher, on D, both times accompanied by differently voiced G major triads. Music is a voice responding to overtones, expressing the heart of its range and a deviation from that center; motion while standing still.
We perceive that motion, a function of nature, because we, too, are functions of nature. It is animal warmth.
