Older adults' low adherence to the national physical activity guidelines may stem from a failure to increase positive affective responses to exercise (e.g., enjoyment). Exercising with personalized, tempo-synchronous music playlists has shown promising effects on physical activity promotion in midlife-to-older adults during a cardiac rehab program. The purpose of this study is to determine how personalized, tempo-synchronous music playlists called rhythmic auditory stimulation (RAS) influence exercise behavior change and affective responses to exercise over 8 months among community-dwelling, sedentary older adults.