Re., Thomas Stern's query about US made recordings of ethnic music.

Thomas, there was actually quite a lot issued, especially during the LP era. Here's a few which come to mind. If I can think of anymore I'll post them.

Old Country Music in a New Land-Folk Music of Immigrants from Europe and the Near East. New World. NW 264
Song of the Shepherd: Songs of the Slavic Americans. LP. New World. NW 283.
You Can Tell the World About This-Classic Ethnic Recordings From the 1920s. Morning Star. 45006.
Across the Fields-Norwegian-American music from Wisconsin. LP. Folklore Village Farm. FVF 201
Leonard Finseth. Scandinavian Old Time Fiddler from Wisconsin. LP. Banjar
Edwin Johnnson-Bruce Johnson-Paul Dahlin. American Swedish Spelmans trio, The: Old Country Folk Fiddling. LP Rounder. 6004
Scandanavian-American Folk Dance Music Vol 1-The Norwegians in Minnesota. LP. Banjar. BR 1825
Early Scandinavian Bands & Entertainers-Historical Reissue of Rare Original 78RPM Recordings. LP. Banjar. BR 1840
Sweden
From Sweden to America: Emigrant and Immigrant Songs. Caprice. CAP 2011        
Stranded in the USA – Early Songs of Emigration. TRIKONT US-0326
World in Our Backyard, The: Ethnic Music of our Neighborhoods. Chubby Dragon. CD 1005
To What Strange Place-The Music of the Ottoman-American Diaspora 1916-1929. CD. Tompkins Square. TSQ 2608.

Not all these are vintage or field recordings of course, but they're still worth listening to. Also, don't forget that Arhoolie has put out a lot of stuff from New Mexico, plus a CD of Texas-Czech Moravian bands.