The general aim of this experiment was to investigate the processes involved in reading musical notation and to study the relationship between written music and its auditory representation. It was of main interest to determine whether musicians are able to develop expectancies for specific tonal or atonal auditory events based on visual score alone. Can musicians expect an “atonal” event or will it always sound odd? Moreover, it was of interest to determine whether the modulations in amplitude of a late positive component (P600) described in previous studies are linked to a general mismatch detection process or to specific musical expectancies. Results showed clearly that musicians are able to expect tonal auditory endings based on visual information and are also able to do so for atonal endings, although to a smaller extent. Strong interactions seem to exist between visual and auditory musical codes and visual information seems to influence auditory processing as early as 100 msec. These results are directly relevant for the question of whether music reading is actually music perception.