Three voices and a guitar. That was the concept when Stephen Stills of Buffalo Springfield, Graham Nash of The Hollies and David Crosby of The Bryds came together as a super group in the late 1960s.

Three voices and a guitar.

That was the concept when Stephen Stills of Buffalo Springfield, Graham Nash of The Hollies and David Crosby of The Bryds came together as a super group in the late 1960s.

It would be all about the harmonies and Stills’ sometimes sweet and often electrifying fretwork.

On Tuesday night at the Bethel Woods Center for the Arts, that concept of those magic voices materialized once again during the start of an acoustic set which featured the classic “Helplessly Hoping” followed by cover versions of The Beatles’ “Norwegian Wood,” The Alllman Brothers’ “Midnight Rambler,” The Rolling Stones’ “Ruby Tuesday” and The Who’s “Behind Blue Eyes.”

This legendary band is coming out with a covers collection of the works of other legendary bands.  And they were in strong voice throughout a two-set performance that featured solo hits, a Neil Young tune and the classic CS&N soundtrack of over 40 years of music.

Playing in the historic setting of Woodstock, CS&N opened up with the Joni Mitchell-penned tune “Woodstock,” with Stills firing off guitar licks like his old friend Jimi Hendrix used to do.

While the three resemble something that could be “in a museum” as Crosby stated, you’d never know it based on how Nash and Crosby tickle the ivories. Stills has lost his vocal range and is often hoarse, but his guitar playing provided a spark anchored by the backbeat of longtime drummer Joe Vitale and bassist Bob Glaub.

After Nash performed “Military Madness,” Crosby came on strong with “Long Time Comin’” before Nash told the audience that the band was going to play a song performed only once on tour. That turned out to be the late 1970s hit “Just A Song Before I Go.” The performance was so crisp that it was amazing that this song was only played once before.

Stills followed that with “Southern Cross,” a 1980s hit which got a big hand from the crowd. Then CS&N paid tribute to longtime bandmate Neil Young as Nash took the harmonica for a sweet version of Young’s “Long May You Run.”

The band ended its first set heavy on the classics.

Crosby nailed “Deja Vu” and then combined with Nash for the epic “Wooden Ships,” both featuring Stills blistering away on guitar that would make Hendrix smile.

The show could have ended there. But the second set is what really showed the vocal firepower that CS&N offers.

That first came as Crosby was showcased — with strong harmonies by Nash — on the classic “Guinnevere” and “Delta.” For a guy given up for dead long ago, Crosby has really cleaned himself up and his vocal range is often dazzling.

The two combined for “Wind on the Water” from their days as a duo in the 1970s before Nash took to the keyboard for the crowd pleaser “Our House.”

Then Crosby got the crowd fired up with his political anthem “Almost Cut My Hair” with Stills once again blasting out an extensive solo.

The band saved its last three songs for the “Woodstock” generation.

Stills put a little gruff into his 1970s solo hit “Love the One Your With” before turning to the Buffalo Springfield classic Vietnam War protest song “For What It’s Worth.”

While the band left out “Suite: Judy Blue Eyes” and “Wasted on the Way,” there was one song that had to be played.

It’s the one in the CS&N songbook that’s timeless and offers a lesson for us all.

That would be “Teach Your Children.”

It’s a nice legacy to leave behind for any generation.