Friday, July 29, 1966 was the second night of Bo Diddley and Quicksilver Messenger Service at the Avalon, on Mouse and Kelley's FD-18.

The pairing recurs through this chronicle's 1966 pages and the reason is worth stating plainly: Bo Diddley's rhythm was the single most borrowed thing in the room. The clave-derived pattern that carries his name, the tremolo guitar, the maracas — the Rolling Stones, the Yardbirds, the Animals and Quicksilver themselves had all borrowed his rhythm without always crediting it, and here he was, thirty-seven years old and eleven years into a Chess Records career, headlining over a local band with no record at all.

Quicksilver in July 1966 had been together roughly a year. John Cipollina's guitar — a Gibson SG through Standel and Fender amps, worked hard with the vibrato arm — was already the most distinctive sound in the city, and the band would not release an album until 1968. Chet Helms booked them constantly on that basis, which is exactly the sort of judgement the Avalon is remembered for.