'Marking a transition in its development between the advanced swing of the early Chicago-era recordings and the increased free-form experimentation of its New York tenure, this album also reveals the first recorded versions of two Ra standards, "Friendly Galaxy" and "Love in Outer Space." Accessible, yet segueing into vanguard territory, this album highlights a fertile period in the Arkestra's history. Looser and more aggressive than its Chicago recordings, these pieces find the Arkestra pushing at the limits of harmony and tonality.' Troy Collins 〔

Solar Differentials'' introduced Art Jenkins, a new "Space Vocalist". Jenkins had sought an audition with Sun Ra a few months before the recording, and sang some rhythm-and-blues tunes for him. Sonny told him that he had a nice voice, but what he was looking for was a singer who could do the impossible ("The possible has been tried and failed; now I want to try the impossible"). Art came back one day when they were recording at the Choreographer's Workshop, and dead set on getting on a record somehow, rummaged through a bag of miscellaneous instruments looking for something he could play. But every time he picked up something, someone in the band would tell him to leave it alone. When no one objected when he pulled a ram's horn from the bottom of the bag he began to sing into it, but backwards, with his mouth to the large opening, so that it gave out a weird sound which he made weirder by moving his hand over the small opening to alter the tone. Sonny broke out laughing, "Now that's impossible!" and asked him to improvise wordlessly on the record.' John F Szwed,〔John F Szwed Space is the Place, Mojo, 2000, p192-193〕