"Mass in F Minor" was released in January 1968 and reached number 135 on the Billboard 200. Photos of the band appeared on the back of the record sleeve, though with the band's previous guitarist James 'Weasel' Spagnola shown, rather than Gannon. The Electric Prunes performed the album's songs in concert just once, at the Santa Monica Civic Auditorium, which Tulin described: From the outset the performance was a disaster. We missed the intro on the first song and it never got any better. Amp speakers blew, charts fell off music stands and everyone was, in general, in a complete state of confusion. Ended up each song turned into one long jam. I think we were, at times, all in the same key. I made my way over to the four celli and four French horns and told them to 'jam in E.' Somehow we would hit a break and James would manage a vocal. Mercifully, this all ended and as we were leaving a few 'fans' said, 'We didn't know you guys were into avant-garde jazz.'