MLA

Horn, Charles Frederick, 1762-1830. [Music book]. Box 822. [circa 1830]. https://collections.library.yale.edu/catalog/10000244.

APA, 6th edition

Horn, Charles Frederick, 1762-1830. (["Box 822"])([circa 1830])[[Music book]]. https://collections.library.yale.edu/catalog/10000244.