Music education scholars have questioned the effectiveness of isolated workshop and conference experiences on improving music teacher practices in the classroom. A model of professional development that potentially addresses these concerns is the professional learning community (PLC). In previous investigations of music teacher PLCs, the researchers functioned as both investigator and facilitator of the PLC. Since the PLC model was designed to be led by the participant members rather than by outside experts, the intention of this study was to investigate three middle school band teachers’ experiences participating in an autonomous PLC. The purpose of this instrumental case study was to examine how PLC participation affected the music teachers and their classroom practices. Data collected in this investigation included multiple interviews with each of the three teacher participants, observations of their PLC meetings, observations of their classrooms, and collection of artifacts related to their PLC. The three themes that emerged from this study were: (a) the middle school band PLC meeting conversations focused on, “What’s the biggest fire?” (b) the middle school band PLC was a balkanized community within the Loon Lake school district, and (c) participants’ values and curriculum were largely aligned. Evidence collected in this investigation suggested that the teachers thought participation in the PLC was meaningful and had led to the creation and improvement of assessments and curriculum used in the Loon Lake middle school band program. Though the PLC experience was rewarding to the participants, this study revealed several challenges encountered by the autonomous PLCs in the field. Further research may help clarify how an autonomous music teacher PLC can maintain a focus on students’ music learning, deprivatize teaching practices, and avoid stagnating conversations about teaching practices.