This experiment tested whether personal choice vs. external assignment of task characteristics moderates the effect of incidental affective stimulation on effort-related cardiovascular response. We expected strong action shielding and low receptivity for incidental affective influences when participants could choose themselves the stimulus color of an easy memory task. By contrast, when the stimulus color was assigned, we expected weak action shielding and high receptivity. As expected, participants in the assigned color condition showed stronger cardiac pre-ejection period reactivity when exposed to sad music than when exposed to happy music during task performance. These music effects did not appear among participants who could personally choose the stimulus color. Our results replicate previous research by showing that personal choice leads to action shielding, whereas individuals remain receptive for affective influences during volition when task characteristics are assigned.