The second is the most tense of the small intervals. The minor second (a semitone) is piercingly painful; the major second (a whole tone) is harder and “prickly.”
Seconds create the effect of terror and unease in cinema: John Williams's famous shark motif in Jaws is built on the repetition of a minor second. In classical music, the “fate motif” in Beethoven's Fifth Symphony also rests on this interval. In jazz, bluesy wandering chords produce second-interval frictions that are part of the style.
The second is the smallest interval of the classical system: a minor second equals one semitone, a major second two (a whole tone). All scales and modes are built from the alternation of tones and semitones, so the second is the brick from which the modal system is raised. Several minor seconds in a row yield chromatic motion, and a dense stacking of seconds forms a cluster — an expressive device of 20th-century music.
