His mother, Frances Yauch, confirmed his death. He had been treated for cancer of the salivary gland for the last three years.

With a scratchy voice that grew scratchier through the years, Mr. Yauch rapped as MCA in the Beastie Boys, who were inducted into the Rock and Roll Hall of Fame this year. They offered many listeners in the 1980s their first exposure to hip-hop. They were vanguard white rappers who helped extend the art of sampling and gained the respect of their African-American peers.

While many hip-hop careers are brief, the Beastie Boys appealed not only to the fans they reached in the 1980s but to successive generations, making million-selling albums into the 2000s. They grew up without losing their sense of humor or their ear for a party beat.

Mr. Yauch (pronounced yowk) was a major factor in the Beastie Boys’ evolution from their early incarnation, as testosterone-driven pranksters, to their later years as sonic experimenters, as socially conscious rappers — championing the cause of freedom in Tibet — and as keepers of old-school hip-hop memories. The Beastie Boys became an institution — one that could have arisen only amid the artistic, social and accidental connections of New York City.

In the history of hip-hop, the Beastie Boys were both improbable and perhaps inevitable: appreciators, popularizers and extrapolators of a culture they weren’t born into.

“The Beasties opened hip-hop music up to the suburbs,” said Rick Rubin, who produced the group’s 1986 debut album, in a recent interview with The Plain Dealer of Cleveland. “As crazy as they were, they seemed safe to Middle America, in a way black artists hadn’t been up to that time.”

The rapper Eminem said in a statement, “I think it’s obvious to anyone how big of an influence the Beastie Boys were on me and so many others.”

The Beastie Boys started their major-label career with two pivotal albums: “Licensed to Ill” (1986), a cornerstone of rap-rock that became the first hip-hop album to top the Billboard chart, and “Paul’s Boutique” (1989), a wildly eclectic, sample-based production that became a template for experimental hip-hop.

The Beasties brand expanded well beyond music: with their own magazine and record label, Grand Royal; with the social activism of Mr. Yauch’s Milarepa Foundation, which produced an international series of Tibetan Freedom Concerts; and with work in film, as Mr. Yauch (calling himself Nathanial Hörnblowér) directed Beastie Boys videos and went on to start Oscilloscope Laboratories, an independent film production and distribution company….More at Adam Yauch, 1964-2012: Adam Yauch, a Founder of the Beastie Boys, Dies at 47