From WILL - Classics of the Phonograph -

Conductors Who Advocated for American Music

During the 1930s and 1940s, not all conductors active in the U.S. were interested in American music, but Serge Koussevitzky and Leopold Stokowski were. Koussevitzky, with the Boston Symphony, was a strong advocate of the music of Aaron Copland and Roy Harris, and Stokowski, with many ensembles, was a tireless champion of a large array of American composers. I'll play some of their best known recordings.