Saturday, August 17, 1968 held both weekend stands at their midpoint — Creedence Clearwater Revival, It's a Beautiful Day, and Albert Collins at Fillmore West under BG-133; Bill Haley and the Comets, the Drifters, and the Flamin' Groovies at the Avalon under FD-133 (per the Bill Graham Foundation Aug-17 page and wolfgangs). The two rooms ran their parallel weekends, the rock-and-roll past at the Avalon and the about-to-break future at the Fillmore, neither yet knowing which of its acts the decade would remember.

Exactly a year later, in the small hours and morning of Sunday, August 17, 1969, Woodstock's third day carried more San Francisco than any other. Janis Joplin — a Family Dog and Avalon fixture in her Big Brother years, now fronting the Kozmic Blues Band — sang around two in the morning; Sly and the Family Stone followed near dawn with the set many remember as the festival's peak; and Jefferson Airplane closed the night as "morning maniac music," taking the stage after eight a.m. into a rising sun (all per the festival performance record on wikipedia, corroborated against setlist.fm). The ballroom scene did not merely attend Woodstock; on the 16th and 17th it substantially was Woodstock.