Abstract: Considering the unique demands posed by music materials and the complexity of cataloguing such documents in a rapidly changing discovery environment, the Music Library Association released in 2012 the first version of Music Discovery Requirements (MDR1), a document specially compiled for music librarians, developers who create and design music discovery interfaces, and related professionals. The revised version, MDR2 was published in 2017. This paper aims to introduce the current situation and experience of music cataloging practice in the United States through an interpretation and analysis of the main content and revisions of MDR, with a view to shedding some light on music resource description in today’s discovery environment.