The purpose of the present study was to investigate the effect of harmonic expectancy violations on emotions. Subjective response measures for tension and emotionality, as well as electrodermal activity (EDA) and heart rate (HR), were recorded from 24 subjects (12 musicians and 12 nonmusicians) to observe the effect of expectancy violations on subjective and physiological measures of emotions. In addition, an electro-encephalogram was recorded to observe the neural correlates for detecting these violations. Stimuli consisted of three matched versions of six Bach chorales, which differed only in terms of one chord (harmonically either expected, unexpected or very unexpected). Musicians' and nonmusicians' responses were also compared. Tension, overall subjective emotionality, and EDA increased with an increase in harmonic unexpectedness. Analysis of the event-related potentials revealed an early negativity (EN) for both the unexpected and the very unexpected harmonies, taken to reflect the detection of the unexpected event. The EN in response to very unexpected chords was significantly larger in amplitude than the EN in response to merely unexpected harmonic events. The ENs did not differ in amplitude between the two groups but peaked earlier for musicians than for nonmusicians. Both groups also showed a P3 component in response to the very unexpected harmonies, which was considerably larger for musicians and may reflect the processing of stylistic violations of Western classical music.