I have just come across these guys, they were "early masters of street pranks and puts-ons. Using hidden microphones, they clandestinely recorded their bizarre encounters with unsuspecting citizens on the streets of San Francisco in the 1960’s" to quote their site. According to their bio "In 1967, Coyle left California to pursue a career in tunneling. He died in 1993 while burrowing under the City of Barcelona."
Their stuff is just such so fresh and funny. Its the mid sixties, pre-hippies, all the targets they talk to are so naive and square. They have got one of the very first portable tape recorders hidden in their suitcase. I'm amazed I had never heard of them before.
The link above takes you to their site, some audio samples are here