It would be difficult to convey to somebody unaware of Crosby, Stills and Nash — if such a person could be found — that trio's impact on the generation that came of age in the late 1960s and early 1970s.

It would be difficult to convey to somebody unaware of Crosby, Stills and Nash — if such a person could be found — that trio's impact on the generation that came of age in the late 1960s and early 1970s.

What's not difficult to understand, but perhaps no less remarkable, is that the group is still making music, and still in demand, 40 years on.

Crosby, Stills and Nash will open the Britt Festivals' 46th season of outdoor concerts Sunday, June 1. It's the only Britt show of the weekend, coming a day after Saturday's "Celebrate Britt" event from 2 to 6 p.m. in downtown Jacksonville, a food, wine and music fete for the venerable festival.

Things will get rolling in earnest on the Britt hillside about a week later, with fusion giants Return to Forever Saturday, June 7, country star LeAnn Rimes Monday, June 9, and New Orleans legends The Neville Brothers and Dr. John Thursday, June 12.

Sunday's Crosby, Stills and Nash show will be just the second gig in a marathon spring/summer tour for the veteran rockers. The tour will commence the night before in Santa Rosa, Calif., and will crisscross the country, visiting 40 venues before wrapping up in Memphis, Tenn., in August. It's the first time CSN has reunited since 2006's Freedom of Speech Tour, which also featured sometime CSN partner Neil Young.

When CSN formed 40 years ago, it was hailed as the first supergroup. This was an era in which the abuse potential of the "super" designation had yet to be discovered. CSN was a "second-generation" group, in that each member had come from a seminal band at a time when the music industry was going through seismic changes.

David Crosby came from The Byrds, Stephen Stills from Buffalo Springfield, and Graham Nash from The Hollies. As if to underscore the "super" part, the group's first album, that self-titled 1969 effort, was an instant classic, containing such hits as Stills' "Suite: Judy Blue Eyes," Crosby's "Guinnevere" and Nash's "Marrakesh Express."

The seeds of the group were planted in 1968, when Crosby had left The Byrds, Buffalo Springfield had disbanded, and Nash was still playing in The Hollies. Crosby, who had produced Joni Mitchell's debut album, was collaborating with Stills, and the two invited Nash, who came through Los Angeles on a Hollies tour, to Laurel Canyon to hear two songs they were working on, "Helplessly Hoping" and "You Don't Have to Cry."

Nash joined the singing that first night, and the planets aligned.

"I thought my heart was gonna jump right through my mouth," Crosby says in a statement he released about the occasion. "It was about the rightest thing I ever heard."

"It was a truly magical moment," Nash adds.

The success of the album brought close harmonies and an acoustic sensibility to a pop world often dominated by electric guitars and monster stacks of speakers.

CSN followed its debut album with "Deja Vu," another classic, with the likes of "Teach Your Children," "Our House," "Almost Cut My Hair" and Neil Young's "Helpless."

After that you pretty much needed a scorecard. CSN broke up in the '70s, but the members kept performing and recording together in various combinations as the years went on, in addition to pursuing their solo projects.

"CSN," a 77-song boxed set, was released in 1991. The group was inducted into the Rock and Roll Hall of Fame in 1997. When they weren't making albums or touring, the members spoke out over the years on behalf of peace, civil rights, the American farmer and other causes and against war and nuclear proliferation.

Stills performed at Britt in July 1995 in a show that had the audience up and dancing. Crosby played a mostly mellow show at Medford's Craterian Ginger Rogers Theater in April 2004 with his son, James Raymond, and local hero Jeff Pevar. Crosby, Stills and Nash performed together at Britt in July 2003.