David Crosby, a folk-rock voice that spanned decades

David Crosby, the outspoken and often troubled singer, songwriter and guitarist who helped create two of the most influential and beloved American bands of the classic-rock era of the 1960s and ’70s, the Byrds and Crosby, Stills, Nash & Young, has died. He was 81. Patricia Dance, a sister of Crosby’s wife, Jan Dance, said in a text message on Thursday evening that Crosby died “last night.” She provided no other details.

Crosby was inducted twice into the Rock & Roll Hall of Fame, as a founding member of the Byrds and as a founder of CSN&Y. He brought jazz influences to both groups, in the process broadening the possibilities of vocally driven folk-rock. And his reach extended to later generations: His alternate tunings became an inspiration for the innovative “freak folk” movement of the early 21st century while influencing scores of other musicians eager to give acoustic music a progressive spin.

If Crosby’s music expanded boundaries, his persona fixed him in a specific era — and proudly so. In 1968, he wrote “Triad,” an ode to free love, recorded in distinct versions by the Byrds, Jefferson Airplane and Crosby, Stills, Nash & Young. His song “Almost Cut My Hair,” which he recorded with CSN&Y for their acclaimed 1970 album, “Déjà Vu,” was a virtual loyalty oath to the counter-culture.

Crosby’s image as the twinkle-eyed stoner and sardonic hedonist of the cosmic age was said to have been a model for the obstinate free spirit played by Dennis Hopper in the 1969 movie “Easy Rider.”

His impish indulgences turned potentially lethal many times. He became nearly as well known for his drug offenses, weapons charges and prison stints as for his music. By the mid-1970s, he was addicted to both cocaine and heroin.

“You don’t sit down and say, ‘Gee, I think I’ll become a junkie,’” Crosby told People magazine in 1990. “When I started out doing drugs, it was marijuana and psychedelics, and it was fun. It was the ’60s, and we thought we were expanding our consciousnesses.”

But later, he continued, “drugs became more for blurring pain.” He added: “You don’t realize you’re getting as strung out as you are. And I had the money to get more and more addicted.”

Crosby’s drug abuse may have exacerbated his medical problems, including a long battle with hepatitis C, which necessitated a liver transplant in 1994. He also suffered from type 2 diabetes and, in 2014, had to cancel a tour to endure a cardiac catheterisation and angiogram.

Despite his health issues, his voice remained robust enough in those years for him to tour. And in his best moments while performing with Stephen Stills and Graham Nash, he could recreate some of the most famous harmonies of the rock era. His voice remained strong as well when touring with his solo band in later years. He was 16 when he received his first guitar, from his older brother, Ethan, who had begun playing years earlier. David started out, like so many others in the early ’60s, performing folk music.

“I would learn two chords and go back and forth between them,” Crosby told the British music magazine Mojo. “What took it to the next level was, my brother started listening to 1950s jazz: Chet Baker, Dave Brubeck, people like that. Listening to jazz really widens your world.”