Music is ubiquitous in our lives. Although we listen to music as an activity in and of itself, music is frequently played while we are engaged in other activities that rely on decision-making (e.g., driving). Despite its ubiquity, it remains unknown whether and how background music modulates the speed and accuracy of decision-making across different domains. We hypothesized that music could affect decision-making through a subjective-timing distortion or via a policy shift toward less-cautious responding. We analyzed response times and accuracy from more than 100-thousand decisions and mapped the effects of music onto decision-process components with a mechanistic model of decision-making. We found evidence supporting the latter hypothesis, by which decisions-across domains-were faster but less accurate with music, and this trade-off was mainly driven by a less conservative decision policy. Overall, our results suggest that background music shapes our decisions by making us less cautious.