Until recently, the Variations Digital Music Library provided online access to approximately 30,000 selected recordings and scores from the Indiana University Cook Music Library. First implemented in 1996 with support from IBM and later revised thanks to grants from the National Science Foundation, National Endowment for the Humanities and the Institute for Museum and Library Services, it served the students and faculty of the Jacobs School of Music until its retirement in January of 2017, prompted by the end of life of one piece of its underlying technology. The recordings hosted in Variations have been migrated to Media Collections Online in 2016. Variations addressed real teaching and learning needs beyond the basic features of discovery and access; migrating the Variations materials to a different tool is only one aspect of the change that this transition represents to Variations users and support staff. Other important aspects to consider are gaps in functionality. Some new features have been implemented in Avalon, the system powering MCO, to address some of the gaps. In this talk we will discuss the transition, the features added to Avalon prompted by the Variations use cases, the remaining functionality gaps we intend to address, and how MCO is being received by faculty and students.