Why does music give us goosebumps?

Some chord progressions, a certain voice, or a particular moment in a song creates a physical sensation — chills, shivers, goosebumps. This is called “frisson.” It happens to about 55–86% of people, and not equally.

What I’ve read so far:

• It seems connected to dopamine release. PET and fMRI studies show activation in the caudate and nucleus accumbens — the same reward pathways triggered by food or money.
• Musical “violations of expectation” seem to be key. The chills often come when a chord doesn’t resolve the way you expected, or when a new instrument enters unexpectedly.
• People who are more “open to experience” (a Big Five personality trait) seem to experience frisson more frequently.

What I’m still wondering:

• Is there evolutionary value to this? Or is it a spandrel — a byproduct of other adaptations?
• Why do some people never experience it at all?
• Can you train yourself to experience frisson more, or is it fixed?