Dissonant endings of chord progressions elicit a larger ERAN than ambiguous endings in musicians.

In major-minor tonal music, the hierarchical relationships and patterns of tension/release are essential for its composition and experience. For most listeners, tension leads to an expectation of resolution. Thus, when musical expectations are broken, they are usually perceived as erroneous and elicit specific neural responses such as the early right anterior negativity (ERAN). In the present study, we explored if different degrees of musical violations are processed differently after long-term musical training in comparison to day-to-day exposure. We registered the ERPs elicited by listening to unexpected chords in both musicians and nonmusicians. More specifically, we compared the responses of strong violations by unexpected dissonant endings and mild violations by unexpected but consonant endings (Neapolitan chords). Our results show that, irrespective of training, irregular endings elicited the ERAN. However, the ERAN for dissonant endings was larger in musicians than in nonmusicians. More importantly, we observed a modulation of the neural responses by the degree of violation only in musicians. In this group, the amplitude of the ERAN was larger for strong than for mild violations. These results suggest an early sensitivity of musicians to dissonance, which is processed as less expected than tonal irregularities. We also found that irregular endings elicited a P3 only in musicians. Our study suggests that, even though violations of harmonic expectancies are detected by all listeners, musical training modulates how different violations of the musical context are processed.