Jazz standard and Billy Strayhorn's "Take the 'A' Train" (1941). With the big bands struggling to keep going during World War II, a shift was happening in jazz in favor of smaller groups. Some swing era musicians, such as Louis Jordan, later found popularity in a new kind of music, called "rhythm and blues", that would evolve into rock and roll in the 1950s. Bebop emerged in the early 1940s, with Charlie Parker, Dizzy Gillespie and Thelonious Monk leading the way. It appealed to a more specialized audiences than earlier forms of jazz, with sophisticated harmonies, fast tempos and often virtuoso musicianship.
John Garcia Gensel named full-time Minister to the Jazz Community; initially Jazz vespers were held at various locations including Central Synagogue. In 1968, jazz ministry had become fully established in Saint Peter's Lutheran Church, on Lexington Avenue in New York City. Jazz musicians including Duke Ellington, Thelonious Monk, John Coltrane, Dizzy Gillespie, Miles Davis, Charles Mingus, Billy Strayhorn attended and played regularly at Jazz vespers. In 1975 Documentary Educational Resources published a portrait of Rev. Gensel which was filmed over the course of 5 years; the documentary records Duke Ellington's last concert and funeral. At Saint Peter's Lutheran Church Rev. Gensel also founded