There wasn't an opening act scheduled for the Peter Paul & Mary concert last night at Constitution Hall, but an informal one of sorts took place out on 18th Street, where several hundred people huddled in the cold for 45 minutes waiting for the tickets they had purchased over the phone.

"There will be many moments during this concert when you can become vindictive about your wait," Peter Yarrow joked at the outset of the concert, apologizing for the 45-minute delay. "This is the moment of retribution."

From the time the trio trotted out on stage, hand in hand, singing "If I Had a Hammer," all was forgiven.

The first half of the two-hour presentation brilliantly rekindled the fires of the '60s folk revival. Backed only by Dick Skes on bass, the group celebrated their past with trademark harmonies, dual guitars and reams of satiric commentary.

Following intermission, each of the members took a solo turn. Peter Yarrow led the audience in a touching remembrance of "Stewball"; Paul Stookey recalled his hapless days as a Greenwich Village impressionist, and Mary Travers paid a beautiful tribute to Paul Robeson with a dramatic reading of "Sometimes I Feel Like a Motherless Child."

When the group gathered on stage again for its finale -- including "Blowin' in the Wind" and "This Land is Your Land" -- the audience jumped to its feet time and time again. Any inconvenience suffered earlier in the evening seemed to matter little.