It has often been remarked that there is no such thing as a neutral emotion. All emotions are either negative or positive. Negative emotions arise when experience falls short of anticipation. You expect your car to start and it doesn't. You expect your cat to greet you at the door and find out that it has been run over. Conversely, positive emotions come about when experience exceeds anticipation. You expect to work all day but are given the day off. You expect to pay a lot of money for something and find that it has been marked down. Because most anticipations are minor ones, and most discrepancies are small, little of our emotional life registers as surges and outbursts. Most emotion bobs up and down as small waves on a sea of motivation. But we experience a feeling of well-being when small positive emotional events occur continuously, and we become depressed or irritable when a train of small negative events accost us.
From these principles, it's easy to see how music generates emotion. Music sets up anticipations and then satisfies them. It can withhold its resolutions, and heighten anticipation by doing so, then to satisfy the anticipation in a great gush of resolution. When music goes out of its way to violate the very expectations that it sets up, we call it "expressive." Musicians breathe "feeling" into a piece by introducing minute deviations in timing and loudness. And composers build expression into their compositions by purposely violating anticipations they have established.
Musical expression is forever at odds with musical structure. Every deviation from an anticipation tend to weaken subsequent anticipation and thereby undercut the impact of further deviations. A momentary shift in tempo brings a tinge of emotion, but at the price of undermining the overall sequence of rhythmic anticipations that keep a piece moving along. When too many deviations fall together, the listener loses track of the underlying meter and ceases to anticipate coming beats forcefully. Similarly, using too many non-scale tones (chromatic tones) tends to obscure tonal centers so that harmonic resolutions lose their impact. For composer and performer alike, music-making is always a tug-of-war between the maintenance of underlying musical structure and the indulgence of musical deviations. With too much deviation, music becomes cloying and incoherent. With too little, music becomes cold and mechanical.
The idea that negative emotions arise from unmet anticipations might resolve the longstanding debate over why chords built on major triads sound "happy" while chords built on minor triads sound "sad." Many critics have insisted that such distinctions must be entirely culturally determined, pointing to the very different responses sometimes elicited from non-Western listeners. Still, that an Indonesian might find a minor chord "happy" does not necessarily mean that emotional response to chords is wholly arbitrary. The Indonesian brings a different harmonic paradigm to his listening—one that is not centered on triads—and so he anticipates harmonic relations in a different way. Within that context, a minor chord might entirely meet his expectations and so would sound "happy." Yet minor chords might still be necessarily unhappy within the triad-based Western harmonic system because they violate anticipations established by that system. The overtones produced by minor triads do not overlap as well as those of major chords, and so minor triads are inherently filled with conflict—that is, with violations of the overtone series that is so important to our harmonic system.
More than a few musicologists have wondered why we continue to find music expressive after we have heard a piece a few times and know where its expressive deviations will fall. Shouldn't we begin to expect a composition's deviations automatically, and so cease to be affected by them?
One explanation is that musical systems, including conventions of harmony and form, constantly reinstate standard expectations. We are taught and retaught that one chord naturally leads to another. The underlying logic of the overall harmonic system forces our expectations along certain lines, no matter how many deviations we have previously encountered. So violations of standard expectations continue to be expressive.
Some psychologists have suggested a neurological basis for this phenomenon. On the assumption that our brains are naturally predisposed to certain musical structures, they posit that modules of cerebral cortex devoted to particular kinds of processing can't help but function in terms of the anticipations and resolutions they were designed for. A module that plots out temporal patterns has no choice but to anticipate the next beat as being in time, no matter how many times it has heard that beat arrive late.
