The Matrix, 3138 Fillmore in San Francisco was an important music venue, integral in developing the San Francisco psychedelic scene, being in close proximity to the Fillmore West venue. Opening in 1965, its history was more chequered than the Fillmore, with changing managements changing the direction of the venue, until in 1972 it became a DJ only bar with no live music.

San Francisco in the mid-1960s was the hub of the LSD and Hippie scene and the cultural and political rebellion of 1967's Summer of Love. The resulting influence of these factors on the artists of the area created the fantastic psychedelic posters of the Fillmore. Art dealer Jacaeber Kastor said of the posters, "They couldn't just tell you the information about the show. They had to tell you what kind of people you might meet, what kind of far out trip you might have or perhaps even reveal the mysteries of the universe. Wow. Quantum mechanics, visual mudwrestling, Acid test pop quiz on a phone pole!"

The artist of this poster, Victor Moscoso, is an American illustrator and comic book artist best known for his psychedelic designs of the 1960s. Born in Spain, Moscoso moved to the States early in his childhood, and went on to study art at Cooper Union in New York City and at Yale University. In 1959 he moved to the west coast of America, attending the San Francisco Art Institute, and remaining to take up a post teaching lithography after his graduation. During the late sixties, he produced concert posters for Bill Graham (at the Fillmore) and the Family Dog (Chet Helms, at Fillmore, and later the Avalon Ballroom). He is also known for his involvement with the underground comics’ scene, and was a regular contributor to Zap Comix.

This gig at the Matrix featured The Wildflower, a San Francisco band big on the psychedelic scene in the late 1960s.