Involuntary switching to task-irrelevant sound change was studied by measuring event-related brain potentials (ERPs) and behavioral performance in a dichotic listening paradigm. Pairs of tones (S1 and S2) were presented and subjects were instructed to ignore S1 (delivered to the left ear) and to make a go/no-go response to the subsequent S2 (delivered to the right ear). On most trials, the task-irrelevant S1 was of standard frequency, but occasionally it deviated from the standard frequency either by a small or large amount. It was predicted that deviant stimuli were automatically detected and that they could involuntarily capture attention. If they lead to attention switching, less capacity should be available for the processing of target tones resulting in impaired processing of S2. As in many previous studies, deviant tones elicited the mismatch negativity (MMN), which is a component of the ERP indicating automatic change detection. Furthermore, targets preceded by a deviant tone elicited a smaller N1 wave and were detected less effectively than targets preceded by a standard tone. This impaired processing of targets following task-irrelevant changes occurred only with short S1–S2 intervals (Experiment I) but not with long ones (Experiment II). The results support a model claiming that the auditory system possesses a change detection system that monitors the acoustic input and may produce an attentional “interrupt” signal when a deviant occurs. The involuntary attentional capture caused by this signal leads to impoverished processing of closely succeeding stimuli.