If you're one of the 3 people on the planet who hasn't heard Adele's "Someone Like You," you're excused from reading this post. Everyone else, listen up: It's all about appoggiatura. Michaeleen Doucleff explains in the Wall Street Journal:
An appoggiatura is a type of ornamental note that clashes with the melody just enough to create a dissonant sound. "This generates tension in the listener," said Martin Guhn, a psychologist at the University of British Columbia who co-wrote a 2007 study on the subject. "When the notes return to the anticipated melody, the tension resolves, and it feels good."
Chills often descend on listeners at these moments of resolution. When several appoggiaturas occur next to each other in a melody, it generates a cycle of tension and release. This provokes an even stronger reaction, and that is when the tears start to flow.
Chill-provoking passages, they found, shared at least four features. They began softly and then suddenly became loud. They included an abrupt entrance of a new "voice," either a new instrument or harmony. And they often involved an expansion of the frequencies played. In one passage from Mozart's Piano Concerto No. 23 (K. 488), for instance, the violins jump up one octave to echo the melody. Finally, all the passages contained unexpected deviations in the melody or the harmony. Music is most likely to tingle the spine, in short, when it includes surprises in volume, timbre and harmonic pattern.
Ms. Doucleff goes on to explain that other scientists have found that emotionally wrought music, even sad music, boosts dopamine output in our brains--which makes us crave it.