Music listening has proliferated in the workplace, yet its effects have been overlooked, and classic investigations offer conflicting results. To advance our understanding, we draw from self-regulation and resource allocation theories to suggest that listening to music has curvilinear effects on attentional focus and performance on work tasks and that willpower belief is a key boundary condition. We test these hypotheses across three studies: a pilot study of 108 employees from a software company who took part in a 2-week experience-sampling methodology study and self-rated their music listening and performance, a laboratory study (Study 1) of 252 undergraduate students in which task attentional focus and objective performance on proofreading tasks were captured across repeated trials while listening to music, and a 3-week experience-sampling methodology study (Study 2) of 247 employees that included a within-person manipulation of music listening (little to no music vs. 1 hr longer than usual vs. 3 hr longer than usual), daily self-ratings of task attentional focus and task performance, and weekly coworker ratings of task performance. We find mixed support for our hypotheses. Time spent listening to music exhibited an inverted, U-shaped relationship with self-rated (pilot study) and objective (Study 1) task performance. Individuals with higher willpower belief maintained higher levels of task attentional focus regardless of the amount of music they listened to (Studies 1 and 2), and the curvilinear relationship of reported music listening with self-rated task performance was more pronounced for individuals who believe that willpower is limited (pilot study and Study 2). (PsycInfo Database Record (c) 2024 APA, all rights reserved).