One of my favorite passages in all of Mozart sounds nothing like him. In the opening bars of his String Quartet No. 19 in C Major, quiet notes from the violins and violas ooze over the halting pulse of the cello. At times, sounds coalesce into weird dissonances as parts seem to grope, perhaps instinctually, toward harmony. Then a tense pause—and a jaunty melody bursts forth as if released by a spring.