MLA

Koch, Frederick R. (Frederick Robinson). Music/Scherzo, piano, A minor. Box 334, folder 1909. 1850 Jun 30. https://collections.library.yale.edu/catalog/17473504.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 334, folder 1909"])(1850 Jun 30)[Music/Scherzo, piano, A minor]. https://collections.library.yale.edu/catalog/17473504.