"Ella Fitzgerald Sings the Duke Ellington Song Book" was the only Song Book on which the composer she interpreted played with her. Duke Ellington and his longtime collaborator Billy Strayhorn both appeared on exactly half the set's 38 tracks and wrote two new pieces of music for the album: "The E and D Blues" and a four-movement musical portrait of Fitzgerald. The Song Book series ended up becoming the singer's most critically acclaimed and commercially successful work, and probably her most significant offering to American culture. "The New York Times" wrote in 1996, "These albums were among the first pop records to devote such serious attention to individual songwriters, and they were instrumental in establishing the pop album as a vehicle for serious musical exploration."