Sunday, August 4, 1968 closed Iron Butterfly, Canned Heat and Initial Shock at the Fillmore West, ending the BG-131 week.

*In-A-Gadda-Da-Vida* had been released that June and was on its way to becoming one of the best-selling albums of the decade — seventeen minutes of it filling the whole of side two, organ and drum solo and a title that exists because the phrase was slurred past recognition in the studio. Iron Butterfly were, briefly, enormous.

Canned Heat beneath them were built by two record collectors, Bob Hite and Alan Wilson, whose knowledge of pre-war blues was genuinely encyclopaedic and who turned it into "On the Road Again" and "Going Up the Country". Both bands played Woodstock the following year; Wilson was dead within two.

BG-131 is another Conklin sheet carrying two headline bills — the Butterfield Blues Band with Santana on the front half, this bill on the back. The poster names a week; the week held two different shows.