Although music plays an important role in the lives of adolescents, the majority of high school students in the United States do not participate in the large performance ensembles traditionally offered in schools. Researchers have suggested that changes to the high school music curriculum, mainly through the inclusion of alternative music courses (e.g., popular music) and musical genres more relevant to students, would encourage more music study in schools. The purpose of this study was to determine whether students who elect alternative music courses were influenced to study music by different motivational factors than traditional large ensemble participants and whether sex influenced participation in alternative music classes. A Musical Motivation Questionnaire was distributed to all music students attending six high schools in Minnesota. Principal components analysis and reliability testing identified the presence of eight motivational factors that influenced students' choices to participate in high school music courses. Results from subsequent statistical analyses revealed that these factors influenced students enrolled in alternative music courses differently than large ensemble participants, influenced female students differently than male students, and that male students were more likely to participate in alternative music courses than female students. These findings suggest that expanding curricula to include alternative music courses may motivate a new or different population of students to engage in the music learning opportunities offered in high schools.