Mendelbaum and Shag closed their Matrix stand on Saturday, September 6, 1969.

A closing night with a one-line listing, for a band whose album would not be released for decades — which makes it a fair place to say what the Matrix was by 1969, because it outlived both ballrooms and is remembered least.

Marty Balin had opened it in August 1965 as a room for the band he was assembling; Jefferson Airplane took their name there on the first night. By the time of this booking Balin was long gone into the Airplane, the Avalon had closed the previous year, the Fillmore West had eighteen months left, and the Matrix was still running — one act, several nights, no poster, a hundred people at most. It closed in 1972.

The club has almost no presence in the visual record this chronicle is built from, because it never printed anything. Its entire surviving trace is the listings: a date, a name, sometimes a second name. That is a real limit on what can be written about any single night here, and stating the limit is more honest than padding around it.