Crosby,Stills, Nash and a not so young crowd celebrated the spirit of the '60s with mixed results at Merriweather Post Pavilion last night. Unlike Paul McCartney, the Grateful Dead and some other acts on rock's seniors tour this summer, CSN was greeted by a crowd that, for the most part at least, was old enough to remember who Max Yasgur was when his name popped up during the encore of "Woodstock." That was one of several performances in which the audience's 7,000 voices nearly drowned out the trio and its five-piece band.

Counting a brief intermission, the show ran more than 2 1/2 hours and improved with time. The first hour was marred by both lackluster vocals -- Stephen Stills's voice seemed particularly frail on "Love the One You're With" -- and several poor choices. The songs off the trio's new album "Live It Up" and some other recent material, including tunes from solo projects, were largely forgettable, and the problem was compounded when the trio turned the '60s political anthem "For What It's Worth" into a campy, if crowd-pleasing, sing-along.

The second and longer set was far more focused, even though it too seldom transcended a certain nostalgic appeal. An acoustic interlude found Graham Nash at the piano quietly reprising "Our House" to thunderous applause, followed by David Crosby, who's looking more and more like Bert Lahr's Cowardly Lion these days, playfully improvising with Nash on "Guinevere." The trio then lavished its trademark harmonies on "Helplessly Hoping," before Stills, who played some marvelous acoustic and electric guitar throughout the night, sparked an extended version of "Wooden Ships" as well as the inevitable "Suite: Judy Blue Eyes" and other favorites.