We present REXband, an interactive music exhibit for collaborative improvisation to medieval music. This audio-only system consists of three digitally augmented medieval instrument replicas: thehurdy gurdy, harp, and frame drum. The instruments communicatewith software that provides users with both musical support andfeedback on their performance using a "virtual audience" set in amedieval tavern. REXband builds upon previous work in interactivemusic exhibits by incorporating aspects of e-learning to educate, inaddition to interaction design patterns to entertain; care was alsotaken to ensure historic authenticity. Feedback from user testingin both controlled (laboratory) and public (museum) environmentshas been extremely positive. REXband is part of the RegensburgExperience, an exhibition scheduled to open in July 2007 to showcase the rich history of Regensburg, Germany.