August 8, 1967 was a Tuesday, and it opened a six-night Fillmore Auditorium run that is one of the great blues-rock convergences of the year: the Electric Flag, Moby Grape, and the Southside Sound System, under Bonnie MacLean's poster BG-77. The University of Delaware finding aid that preserves the BG-77 record lists the full span — August 8 through 13 — and the shifting bill across it, which is where this run gets interesting.

The headliner was Mike Bloomfield's Electric Flag, and August 1967 was very nearly the band's public beginning. Bloomfield had left the Paul Butterfield Blues Band to build "an American music band" with horns — Buddy Miles on drums, Nick Gravenites and Barry Goldberg, Harvey Brooks on bass — and the group had made its true debut two months earlier at Monterey Pop. To catch them at the Fillmore in August, still new, still a rumor as much as a band, was to catch the Bloomfield project at its most promising, before the internal troubles that would break it apart within a year.

The run's second headliner tells its own small story about how fluid these bills were — and how uncertain the record can be. Moby Grape — the San Francisco band Columbia had just launched with the notorious five-singles-at-once campaign — was billed early in the BG-77 run, and by August 10 it was also opening its own headline stand across town at the Avalon under Victor Moscoso's FD-75. That overlap is a genuine, unresolved puzzle: Corry Arnold, the scene's most careful chronicler, books Moby Grape at the Fillmore through August 10 while the Avalon poster simultaneously bills them August 10–13, and he flags August 10 as a two-venue conflict nobody has settled rather than a clean hand-off. What the BG-77 poster shows is that the Steve Miller Blues Band was added to the bill for the back half of the run (the University of Delaware finding aid lists Steve Miller alongside the Electric Flag on the same sheet), which is the likeliest way the Fillmore covered Moby Grape's departure to the Avalon — but the exact night Moby Grape stopped playing the Fillmore is not documented, and we say so rather than invent a tidy switch. The Southside Sound System (sometimes "South Side Sound System") played all six nights. The lesson is the opposite of reassuring: a single poster printing "Moby Grape" for a six-night run tells you who was advertised, not who stood on which stage on which night.

August 8 in other years is quieter. In 1968 it was the Thursday closing night of the Chambers Brothers / Charlatans / Queen Lily's Soap front-half of the Fillmore West's BG-132 (Lee Conklin's single six-night poster, which the chronicle heroes on its August 6 opening) — a solid night but a continuation rather than a new event. In 1966, the Matrix club was in the middle of a Little Walter engagement, the Chicago blues harpist backed by the house and, later that week, by Quicksilver Messenger Service, whose August 9, 1966 tape from the Matrix is the earliest known live QMS recording. The Avalon, meanwhile, was dark on August 8, 1967 — between the Charles Lloyd run (FD-74, closed August 6) and the Moby Grape run (FD-75, opening August 10) — a two-night gap that itself is worth noting, because the ballroom calendar was not yet the seven-nights-a-week machine it would become.

But the day is Electric Flag's. Opening night of BG-77 at the Fillmore Auditorium, Bloomfield's new band on a Bonnie MacLean poster, with Moby Grape passing through for two nights on its way to the Avalon — August 8, 1967 catches three of the scene's restless summer bands crossing paths on a single Tuesday.