MLA

Koch, Frederick R. (Frederick Robinson). Music/Toccata, violin, piano. Box 340, folder 1991. [1922-23]. https://collections.library.yale.edu/catalog/2012101.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 340, folder 1991"])([1922-23])[Music/Toccata, violin, piano]. https://collections.library.yale.edu/catalog/2012101.