Peter Tork, the Monkee known for his self-effacing humor, died today. He was 77.

His sister confirmed his death to the Washington Post, but offered no details. Tork had undergone surgery in 2009 for a rare cancer of the tongue, but resumed his career within months and toured with Mickey Dolenz, Davy Jones (before his death) and Mike Nesmith for much of the decade since.

However, without offering details, he chose not to join Dolenz and Nesmith on their most recent tour.

Beloved, yet mocked as “The Pre-Fab Four,” The Monkees were signed to play a fictional rock and roll band on a mid-1960s sitcom. They had a string of hit records and sold-out concerts. But when sunshine pop fell out of favor near the end of the decade, so did The Monkees.

In 1969, Tork became the first to quit the group. He, Dolenz and Jones reunited occasionally, especially to mark the foursome’s 20th, 30th and 45th anniversaries. Jones’s death in 2012 led to Nesmith’s return to the fold for tours that fall and again in 2013.

Born Peter Thorkelson in Washington, D.C., he was the son of an Army officer who became a professor at the University of Connecticut. A folk music artist who moved to New York in the early ’60s, both he and his pal Stephen Stills auditioned for The Monkees, when they learned of the rock-sitcom project.

Tork told Guitar World magazine in 2013, “I refute any claims that any four guys could’ve done what we did… There was a magic to that collection. We couldn’t have chosen each other. It wouldn’t have flown. But under the circumstances, they got the right guys.”