Social cognition research suggests that incidental, environmental stimuli (e.g., business suits) can nonconsciously influence the degree to which behavioral dispositions (e.g., competitiveness) are expressed. Similarly, cognitive research suggests that incidental action-related objects (e.g., hammers) can prime action plans that then affect the speed with which a concurrent, intended action (e.g., power grip) is executed. However, whether incidental stimuli can instigate actions that run counter to one’s current goals has yet to be determined. Moving beyond indirect effects, we show that such stimuli can directly cause the expression of undesired actions: Incidental stimuli resembling musical notation caused the systematic expression of unintended key presses in musicians, but not in nonmusicians. Moreover, the effect was found even when targets and distracters bore no apparent perceptual or semantic relation. We discuss the implications of these findings for models of action production and for social-cognitive concepts (e.g., applicability) regarding the limits of nonconscious processing.