In 1936, De Paur became the musical director of the Negro Unit of the Federal Theater Project in New York City.

In 1941 he collaborated with the conductor Alexander Smallens and the orchestral accordionist John Serry Sr. in an oratorio production of Virgil Thomson's opera Four Saints in Three Acts at New York City's Town Hall.

[4] De Paur enlisted in the United States Army Air Forces in 1942, was promoted to Lieutenant, and became the music director of the play Winged Victory.

In the early 1960s, the De Paur Chorus was formed to tour 18 African nations under the United States Information Agency.

[2] Shortly after the chorus disbanded in 1968, De Paur became the associate director of the Lincoln Center International Choral Festival.