Defined as the ability to engage in music activities on one's own, musical independence is a frequent goal of music education. This yearlong study investigated musical independence within concert bands through interviews and observations of participants of secondary programs that included musical independence as a primary objective. Constructivist grounded theory analyses of the participants' experiences led to a model of musical independence that included three interrelated outcomes: student agency, critical decision making, and lifewide/lifelong musicianship. These outcomes were the result of specific instructional practices that utilized cognitive modeling, scaffolded instruction, and authentic, regular, student-led music-making in curricular ensembles to promote student agency and decision making. These instructional practices relied upon preconditions for independence, including musical, social, and 21st-century skills foundations frequently found in large-ensemble classrooms. This study provides a model that can be situated within current large-ensemble practices to support the development of musical independence.