OKLAHOMA!, the first Rodgers & Hammerstein musical, was also the first of a new genre, the musical play, blending Rodgers' sophisticated style of musical comedy (which he had perfected in a twenty-five year partnership with lyricist Lorenz Hart) with Hammerstein's innovations in operetta (conceived in collaboration with such composers as Sigmund Romberg, Vincent Youmans, Rudolf Friml and Jerome Ke