There comes a moment at a concert. Suddenly, things begin to click onstage. And the audience knows it.

Like when James Taylor and Carole King, old friends but never really musical collaborators, started goofily bouncing in unison Tuesday at Xcel Energy Center during Danny Kortchmar's guitar solo in "Smackwater Jack." Even when the bit was done, Taylor kept going with playful knock-kneed dancing. He and King were obviously into it, clearly having fun -- well, as much fun as 60-something performers are allowed onstage (unless they're named Bruce Springsteen, Neil Young or Mick Jagger).

At song's end, Taylor reached to grab the acoustic guitar out of King's hands (she usually plays piano) before a roadie collected it. At that moment, Taylor and King felt like collaborators, band mates, partners. Finally.

Their two-hour-plus, two-set performance was pleasingly nostalgic, thrilling 18,000 baby boomers who were getting high on the fumes of their (take your pick) adolescence, college years or first marriage. But the Taylor-King concert wasn't always smartly staged or musically collaborative, especially in the first half.

Performing on a revolving in-the-round stage, King and Taylor were usually stationed next to (or near) one another, meaning there was always a backside to the stage. So too many people were forced to watch this show on giant video screens over the stage. Putting the stars on opposite sides of the stage might have been more visually compelling.

What was more compelling, especially in the second set, was when Taylor, 62, and King, 68, actually performed as a duo. It started on an old Everly Brothers hit that Taylor had recorded with Art Garfunkel and that King happened to have co-written. Sitting next to each other on stools, they cooed "Crying in the Rain" like the Everly Brother and Sister. As they harmonized, she made moon eyes at him. Then she leaned her head on his shoulder. Shy Ol' James just continued to play his acoustic guitar. When the song was over, she hugged him and then he nuzzled her curly noggin.

King and Taylor, who became friends in 1970 in Los Angeles' burgeoning singer-songwriter scene, were looser and more talkative in the second and better half of the show. Not that the first segment should be overlooked, especially King's "Natural Woman," when she cut loose like Aretha's baby soul sister (though she didn't play piano on this, one of her signatures).

In the latter set, Taylor shifted into third gear on "Steamroller," always a rockin' blues favorite (well, rockin' for him) at his concerts. And then King, backed by what is essentially Taylor's touring band, got bluesy on "It's Too Late."

If someone had an Applause-o-meter Tuesday, King, who has seldom toured, clearly registered higher than Taylor, who has been a road warrior and frequent Twin Cities visitor. But whenever they got involved on each other's songs -- such as his harmonizing on her "Will You Still Love Me Tomorrow" or a duet version of "You've Got A Friend" that ended with a heartfelt hug and the closing, cuddly lullabye for two, "Close Your Eyes" -- those were moments that were as magical as they were nostalgic.

For a set list, go to Jon Bream • 612-673-1719