Herbie Hancock recorded this album in 1970, in the early days of the jazz fusion movement, and was still transitioning from post bop and avant-garde jazz to fusion. The first thing he did was use electronic instruments and experiment with the jazz song format. This is the first album with the Mwandishi Sextant, where every member had a Swahili name attributed to them (Mwandishi was Herbie's name).The album has 3 very different tracks. “Ostinato (Suite for Angela)”, is composed by an ostinato (riff for the rockers) in 15/8 time signature, and the whole band builds upon that continuous and hypnotic riff , with improvisation and dynamic changes. “You'll Know When I Get There” is quite smooth and calm, if we compare with the other two songs. “Wandering Spirit Song” is an almost free jazz song, that as so much tension, that the listener tries to gasp air in the release moments. This is a mystical album, and should be listened as such.