Musicians are highly trained motor experts with pronounced associations between musical actions and the corresponding auditory effects. However, the importance of auditory feedback for music performance is controversial, and it is unknown how feedback during music performance is processed. The present study investigated the neural mechanisms underlying the processing of auditory feedback manipulations in pianists. To disentangle effects of action-based and perception-based expectations, we compared feedback manipulations during performance to the mere perception of the same stimulus material. In two experiments, pianists performed bimanually sequences on a piano, while at random positions, the auditory feedback of single notes was manipulated, thereby creating a mismatch between an expected and actually perceived action effect (action condition). In addition, pianists listened to tone sequences containing the same manipulations (perception condition). The manipulations in the perception condition were either task-relevant (Experiment 1) or task-irrelevant (Experiment 2). In action and perception conditions, event-related potentials elicited by manipulated tones showed an early fronto-central negativity around 200 msec, presumably reflecting a feedback ERN/N200, followed by a positive deflection (P3a). The early negativity was more pronounced during the action compared to the perception condition. This shows that during performance, the intention to produce specific auditory effects leads to stronger expectancies than the expectancies built up during music perception.