At the Matrix on Friday, September 5, 1969, Mendelbaum's stand continued with the second act changed for the weekend: Shag replaced Womb.

By 1969 the Matrix was booking a different kind of week from its 1966 self. The room that had built Jefferson Airplane four years earlier was now largely a proving ground for Bay Area bands who would not get a ballroom headline — short runs, rotating support, and almost nothing printed. Mendelbaum were one of those: a local group who recorded an album that went unreleased for decades. Womb, whom Shag replaced this night, were on a Fillmore West bill two miles away the same month, third under Spirit on David Singer's BG-189.

That circulation is the ordinary texture of the scene in its late phase — the same second-tier bands moving between the big hall and the small club within a single week, most of them a year or two from dissolving without a record anyone would hear.

The Matrix itself lasted until 1972, outliving the Avalon by four years and the Fillmore West by one.