Underneath soft blue stage lights and a handsome “CS&N” logo, harmony experts David Crosby, Stephen Stills, and Graham Nash casually walked on stage on Tuesday evening (Aug. 18), smiling and grinning at each other. The house was almost completely packed with a healthy mix of longtime fans (some of whom looked pretty elderly!), dedicated hippies, aging yuppies, college kids, and local musicians. The applause roared as the trio slid into the opening number “Helplessly Hopeful.” What some had expected to be a low-key folk-rock recital turned out to be a full-on, hit-laden rock concert.

It had been 40 years since Crosby, Stills, and Nash released their landmark 1969 self-titled debut album — and almost exactly 40 years since the band’s national live debut at the Woodstock Festival. They looked older, wiser, totally at ease. Vocally, their pipes sounded a little rusty, with Stills and Crosby warbling a bit on the lower-toned harmonies. Luckily, it only took them three songs to warm up. “Let me thank you all for coming here … and spending money on us,” joked Crosby. “I’m honored to be here.” The feeling was mutual, as many in the audience looked genuinely honored and thrilled to be watching one of their favorites.

A quartet of backing musicians slipped on and off the stage between songs during the acoustic-based portion of the first set. “These are some quiet songs, but we’ll get loud a little later,” announced Nash. He wasn’t kidding. Things accelerated from song to song as Nash and his mates switched instruments, traded licks, sang with increasing smoothness, and built momentum. A delicate rendition of “Time Wasted in The Way” led into a mini-set of covers of “artists we love,” as Crosby put it, including reworkings of the Stones’ “Ruby Tuesday” and James Taylor’s “Close Your Eyes,” plus a slow-moving but steady version of Grateful Dead’s “Uncle John’s Band.” A mellow duo performance between Nash and Crosby of “Guinnevere” marked the end of the quiet portion and the beginning of a lengthy crescendo.

Musically, the band’s stage sound filled in as they went, with additional drum work, Hammond B3 organ chords, and piano from the backing band. At one point Stills switched from guitar to bass (and he even did an eight-bar solo at one point on Crosby’s “Dream for Him”). The big man sounded a bit raspy on the microphone, but his rhythm and lead guitar skills were terrific — especially his more spacious solos on the big hollow-bodied six-strings. His solo on the surprise offering of “Almost Cut My Hair” soared. His sweetly distorted tones were like icing.

The most limber and animated of the three, Nash delivered spirited harmony on the lengthy “Deja Vu” and strong lead vocals on the crowd favorites “Our House” and “Marrakesh Express.” Other highlights included a muscular, full-band rendering of “Southern Cross” and the second-set closer “Wooden Ships.” The crowd demanded two encores and got ’em with a rousing version of “Woodstock” (“We never play this song on tour, but we’re doing it for you tonight since it’s a special occasion,” announced Crosby), and a finale of “Teach Your Children,” which included two full verses sung entirely by the audience.