Playing a musical instrument changes the anatomy and function of the brain. But do these changes persist after music training stops? We probed this question by measuring auditory brainstem responses in a cohort of healthy young human adults with varying amounts of past musical training. We show that adults who received formal music instruction as children have more robust brainstem responses to sound than peers who never participated in music lessons and that the magnitude of the response correlates with how recently training ceased. Our results suggest that neural changes accompanying musical training during childhood are retained in adulthood. These findings advance our understanding of long-term neuroplasticity and have general implications for the development of effective auditory training programs.