We developed the Open Orchestra system to provide individual musicians with a high-fidelity experience of ensemble rehearsal or performance, combined with the convenience and flexibility of solo study. This builds on the theme of an immersive orchestral simulator that also supports the pedagogical objective of instructor feedback on individual recordings, as needed to improve one's performance. Unlike previous systems intended for musical rehearsal, Open Orchestra attempts to offer both an auditory and a visual representation of the rest of the orchestra, spatially rendered from the perspective of the practicing musician. We review the objectives and architecture of our system, describe the functions of our digital music stand, discuss the challenges of generating the media content needed for this system, and describe provisions for offering feedback during rehearsal.