From the website:
"Folklife is an integral part of all American lives and an essential part of the National Library. The story of America is reflected in the cultural productions of ordinary people who live everyday lives, from cooking and eating meals, to the activities of work and play, to religious observances and seasonal celebration. Folklife includes the songs we sing, the stories we tell, the crafts we make. The American Folklife Center was created in 1976 by the U.S. Congress to "preserve and present" this great heritage of American folklife through programs of research, documentation, archival preservation, reference service, live performance, exhibition, publication, and training. The American Folklife Center was made permanent in 1999. The Center includes the Archive of Folk Culture, which was established in the Library of Congress in 1928, and is now one of the largest collections of ethnographic material from the United States and around the world."
The Center has several Yiddish holdings and relevant literature. See for instance:
It is advisable to contact the Center as the website does not give a complete overview of its holdings. A draft of the Jewish, Yiddish, and Hebrew collections is available upon request.
At the moment the Yiddish radio archives collected by Henry Sapoznik (founder of Living Traditions) are being transferred to the Center. See also the webcast of a presentation by Henry Sapoznik entitled Hear, O Israel: Yiddish-American Radio 1925-1955.