Introduction You're in the middle of an ordinary day — driving, washing up, waiting for something — and a song comes on. Within seconds, something shifts. Your shoulders drop. Your breathing slows. The thing you were anxious about a moment ago hasn't changed, but somehow you're holding it differently. This happens to almost everyone, so often that we stop noticing it. We chalk it up to mood, or memory, or just liking the song. But what's actually happening in your body in tho