[1][2][3] Slugs' Saloon, which opened in 1964, was a small club in the Lower East Side of Manhattan, and had a reputation for being conducive to the presentation of adventurous music.

Ayler frequently played there during 1965 and 1966,[4] and Sun Ra's Arkestra performed there every Monday night beginning in March 1966, and continuing for eighteen months.

[5] Slugs' was also known as a dirty and dangerous place located in a rough area,[5] and was described by jazz critic Bill Smith as featuring "spit and sawdust" with knife-wielding audience members.

[2] According to bassist and Ayler biographer Jeff Schwartz, the May 1, 1966 recording heard on the album is "an authorized bootleg, a tape made by an audience member," with poor sound quality and mis-labeled song titles.

However, Schwartz also wrote that the album is "essential" in that it "shows the beginnings of profound change in Ayler's music, and it represents a structural experiment... that is exceptional within his recordings."

[2] In a review for AllMusic, Scott Yanow described the music as "both futuristic (with extroverted emotions expressed in free improvisations) and ancient (New Orleans marching band rhythms, group riffing, and folkish melodies)".

Jurek called "Our Prayer" "an atonal fury of pure gospel shouting and blues hollering to the heavens", and referred to "Bells" as "truly astonishing" and "Ayler's masterpiece", stating: "By 16 minutes the cover has melted from your skull and the sun is shining from within and without and you have been transformed forever.

"[6] In an article for Pitchfork, Mark Richardson described the music as "long medleys where one song segued into the next, and the wild energy of [Ayler's] earlier solos were being channeled into unbearably intense statements of melody.

"[4] Writing for All About Jazz, Francis Lo Kee commented that the album "offers catharsis", and wrote: "This music as a whole doesn't use harmony as a basis for improvisation.