Violations of expectancies in the processing of complex regularity-based musical contexts are reflected in the ERAN. The ERAN is larger in adults with formal musical training (musicians) than in those without, reflecting that more specific representations of musical regularities lead to more specific musical expectancies. The purpose of this study is to investigate effects of musical training in children. Therefore we conducted a music experiment with chord sequences ending either with a (regular) tonic or with a (irregular) supertonic chord. Comparing two groups of subjects with and without musical experience at different ages, we expected a larger amplitude for the ERAN for the groups with musical experience. The difference between the groups should increase with age because of the longer lasting experience with the learned instrument.