This paper discusses how the Howard B. Waltz Music Library and the University of Colorado Boulder’s Metadata Services Department cooperated to resurrect and complete a long-dormant retrospective conversion cataloging project involving musical scores and vinyl records. It addresses the resources that both groups brought to the relationship; the collaborative process by which decisions were made; the implementation plan and challenges; and how fostering a culture of customer service within the Metadata Services Department contributed to the project’s success. It also contrasts Colorado’s project with two other cooperative music cataloging projects and explains how its approach can serve as a model to other libraries who have significant cataloging backlogs or hidden collections but may feel hindered by the lack of specialized in-house cataloging expertise.