 The Free Spirits have sometimes been cited as the earliest jazz-rock band.During the late 1960s, at the same time that jazz musicians were experimenting with rock rhythms and electric instruments, rock groups such as Cream and the Grateful Dead were "beginning to incorporate elements of jazz into their music" by "experimenting with extended free-form improvisation".Other "groups such as Blood, Sweat & Tears directly borrowed harmonic, melodic, rhythmic and instrumentational elements from the jazz tradition".