He peppered his talk with oft-told hip-hop tales and intriguing nuggets of cultural history. He told hip-hop's creation story, of the famous 1973 party in the Bronx, at 1520 Sedgwick Avenue in Morris Heights, whose host was the legendary Jamaican immigrant disc jockey, D.J. Kool Herc. He described how the looting of hi-fi stores during the 1977 New York City blackout propelled D.J. culture. ("It was like Christmas for black people" he said. "The next day there were a thousand new D.J.'s.")

He played charmingly primitive early rap records, like the Fatback Band's "King Tim III (Personality Jock)" (widely regarded as the genre's first single) and songs by the Sequence, one of the earliest all-female rap ensembles. He waxed rhapsodic over hip-hop's humble beginnings, when the biggest rap shows in New York were announced on hand-lettered Xeroxed fliers (Caz distributed several vintage examples), and D.J.'s powered their sound systems for outdoor block parties by tapping into the wiring of street lamps.

"The rappers today who can drive around in Bentleys, with their jewelry and million-dollar homes," Caz told the tour group. "They're able to live like that because cats like me and Bambaataa" -- the famous rapper and D.J. Afrika Bambaataa -- "were in the trenches back in the day, laying the groundwork and getting chased off the block by the police."

That sense of grievance is common among old-school rappers and D.J.'s. "All of the pioneers that I know feel overlooked and dissed," said Ms. Harris, whose tour guides have also included Rahiem of the Furious Five and Reggie Reg of the Crash Crew. Of course, long-term memories are rare in popular music, and hip-hop M.C.'s and producers are particularly unsentimental about the musical past. For good reason: it is precisely that ruthless fixation on novelty -- new sounds, fresh styles, the next big thing -- that has kept the genre vital for so long.

"We have a real thing in hip-hop about out with the old, in with the new," Ms. Harris said. "I'm shocked about how little awareness of history there is, especially since so many people are making so much money in the rap industry. There's much more awareness of hip-hop history in other countries."

Artists like Grandmaster Flash tour regularly overseas, where they draw far bigger audiences, and Ms. Harris estimated that 80 percent of Hush Tours' patrons are "international visitors." Sure enough, a recent tour included just four Americans, along with tourists from England, France, Germany, Australia and Kenya. In this respect, old-school rappers and D.J.'s have in recent years become similar to jazz musicians, who have long experienced rapturous receptions in Europe and Japan while struggling at home to find respect and decent-paying gigs.