Sketches of Spain, though one of Davis's most commercially successful sessions, is also one of his most controversial. Re-teaming with arranger and composer Gil Evans, who played such a pivotal role in Davis's 1949 Birth of the Cool recordings, Davis recorded a series of large group albums beginning in the late '50s, including Porgy and Bess, Miles Ahead, and Quiet Nights. Sketches of Spain, with its emphasis on flamenco, rich orchestrations, and relaxed tempos, is certainly one of Davis's most mellow recordings (he even works out on fluegelhorn), and proved to have broad appeal. To some critics, however, the project was elevated elevator music.