An early right anterior negativity (ERAN) is one of the event-related potentials (ERPs), which has been thought to reflect the harmony processing. However, the nature of the cognitive processes which is reflected by the ERAN cannot be understood clearly. In this study, the hypothesis that the ERAN is evoked by the stimulus deviated from the expectation by tonal hierarchy was assessed. ERPs were recorded from 12 participants listening harmony and melody sequences. ERAN was observed to the deviated chord in the harmony, but not to the deviated tone in the melody. The close relation between ERAN and tonal hierarchy was suggested.

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