Synanon was originally a drug treatment/rehabilitation facility in Santa Monica, California, started by Charles Dederich in 1958. As time went by, things got weirder and weirder - in 1967 Dederich declared that none of the "patients" could ever leave, and Synanon basically became a religious cult. It became more and more violent - horrifyingly so, really. Here's a detailed history, for those who are interested.
But early on, some excellent jazz musicians went through the program at Synanon; the great saxophonist Art Pepper was probably the most famous resident. In 1961, before Pepper's tenure, Richard Bock of Pacific Jazz Records decided to record some of the Synanon musicians for an album. The most well-known at the time was pianist Arnold Ross, whose career stretched back to the 1940s and big bands - he led a great recording session with Benny Carter on saxophone in 1946. Ross was always an interesting and imaginative player, and he's very good here, at approximately the halfway point of a long playing career.
But Sounds of Synanon helped put one musician on the path to a distinguished career in the jazz business: guitarist Joe Pass. He had made a few recordings before this, but his playing here really caught the critics' ear, and led to a recording contract with Pacific Jazz. He didn't even own a guitar at the time (he was in drug rehab, after all), and the liner notes thank the Fender company for donating a guitar and amp. The back cover picture shows Pass playing a solid-body Fender Jazzmaster - which, in spite of the name, was far from the kind of hollow-body jazz guitar he probably would have preferred. No matter - his playing is might impressive.
The other musicians on the album are competent, to varying degrees, but not really on the same level as Ross and Pass. The adjective that came to my mind to collectively describe them was "unfinished." None of them ever recorded again, as far as I can tell. I can only hope that they escaped Synanon before things really got bad.
Sounds of Synanon was never reissued in the U.S., but there have been CD reissues in Japan and Europe. Someone has put the entire album on YouTube, so here it is.