MLA

Koch, Frederick R. (Frederick Robinson). Music/Unidentified/Waltz for orchestra in E major. Box 330, folder 1857. n.d.. https://collections.library.yale.edu/catalog/12218980.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 330, folder 1857"])(n.d.)[Music/Unidentified/Waltz for orchestra in E major]. https://collections.library.yale.edu/catalog/12218980.