trigger an emotional response
This is really what I meant in my post above.
- It might be just the right groove when you're on a dance floor.
- It might be a killer lyric that really homes in on something meaningful to you.
- It might be a particular choice of synth sound that you particularly love.
- It might be a singer delivering a killer performance.
Lots of ways. I think as musicians, in some ways while we're more cynical ("Oh good grief, another I-IV-V chord sequence in C", "Wow, D50 preset there, hardly original", "Ah, that whole song is a Garageband loop" and so on), but because we're very close to music, there are additional ways we can be triggered because the music matches things we personally like - sound, arrangement and melodic choices, even production choices and so on.*
But basically, different music triggers different things in different people. As long as it's doing *something* good to *someone* (even if it's just the composer!), then it has some worth. I tend to find melody and harmony has more weight to me than rhythm, and I know people who are the other way around.
* One thing I particularly like is when a musician makes a choice that is completely different to how my brain works, and takes me by surprise. I remember one track had a little simple guitar solo, but the way it was phrased kinda broke my brain, in that it just did something that I would never have come up with. Instead of ending the phrase when my brain would be saying "that feels musically complete and satisfying" it continued the phrase for a three more notes. It was such a simple thing, but it really ran across and broke down some brain borders I had without really realising it. I love stuff like that!