While volunteering for KPFA as a recording engineer during this period, he met bluegrass banjo player Jerry Garcia. Despite seemingly opposite musical interests, they soon formed a friendship. Following a brief period as a Post Office Department employee and keno marker in Las Vegas (initially rooming with Constanten, who soon departed to study under Berio and other members of the Darmstadt School in Europe); a second stint with the Post Office in San Francisco; and a collaboration with the likes of Reich, Jon Gibson and Constanten upon the latter's return from Europe under the auspices of the San Francisco Mime Troupe, Lesh was talked into becoming the bassist for Garcia's new rock group (then known as The Warlocks) in the fall of 1964. This was a peculiar turn of events, as Lesh had never played bass before. According to Lesh, the first song he rehearsed with the band was "I Know You Rider". He joined them for their third or fourth gig (memories vary) and stayed until the end.