"Beach Blanket Babylon" is closing down this year after a 45-year run. But as impressive as that is, there's an even longer-running performance in SF that's still chugging along: Audium, first created in 1967.

Audium takes place in a specially designed theater that it has occupied since the early '70s, near the corner of Bush and Franklin streets. Equipped with 176 speakers, it takes audiences on an hourlong sonic trip in complete darkness, shifting sounds around, above and below them.

It's the labor of love of a father-son team. Stan Shaff was the original creator back in 1967, and his son David now runs the theater and co-composes the music. Tonight, the Shaffs will unveil Audium's 11th composition, which was two years in the making.

"The idea behind it is to take the listener into their subconscious," David said. "We start on the surface of a scene in a cafe, and go below that scene, and explore what lies under the surface."

Every element of Audium is crafted to fully immerse the audience in sound, from the entrance lobby to the bathrooms to the lighting. The darkness allows listeners — the space accommodates about 50 of them — to hone in on their auditory senses, tuning out other stimuli.

"People get very meditative, and relax," David said. "People evoke dreams, things from the past. It's a real world of sound that we take people into."

Audium founder Stan Shaff in the auditorium. | Photo: Mark Akamine

Audium was born out of the famed Tape Music Center, and the work of Terry Riley, Morton Subotnick, or Pauline Oliveros with recorded sounds. It also belongs to a tradition of large-scale speaker installations, inspired by Edgar Varese's 1958 poeme electronique with 400 speakers, or Karlheinz Stockhausen's Spherical Concert Hall, from the 1970 World Expo in Osaka, which featured 50 speakers.

The music for the new show is a mix of field recordings, natural sounds and electronic sounds, David said. "My aesthetic is more field recordings, and my dad works with electronic music, musique concréte. When I was little, I thought that everyone had a dad walking around with a microphone."

For now, the Shaffs are the sole designers of Audium's soundscape, but they're hoping to begin opening up their theater as a platform for others to create with and use their tools.

"For a long time, it was a personal project, a passion project," David said. "Now, there are a lot of people composing spatial audio works. We're very interested in bringing in people who want to compose for the space."

Audium's new show launches tonight, November 22, and will continue for an indefinite run. Shows are held each Friday and Saturday at 8:15 p.m., along with select Thursdays. Tickets are $20.