When a performer says he and his band are going to "have an old-school party," it's often just talk.

But when Prince says it, dude, you'd be better be ready to party.

When he told fans at Friday's concert at Mohegan Sun Arena to put down their cellphones, clap their hands and dance, fan after fan obeyed.

The opening night of Prince's three-concert stop at Mohegan Sun was the first time Prince has played here, and this is a standalone gig — so you'd hope it would be special. Boy, was it. Prince went all-in for his blazing 2½ hour show.

He kept true to his dance-party vibe, churning through groove-happy song after funk-fueled number. The highlight had to have been the extended jam on "Musicology," which went on for ages but never overstayed its welcome. The whole band — possibly 21 musicians in all, but who could be sure, considering the crowded and ever-shifting configuration — played with loose, infectious joy, and those who could dance did. In the middle of "Musicology," Prince yelled out, "Keep it funky now." No need for that reminder; they had it covered.

Prince's appreciation of the musicians — a combo of his 3rd Eye Girl and New Power Generation groups — seemed wonderfully sincere. He luxuriated in their work, giving individuals a chance to step into the limelight.

As for Prince himself? He's still His Royal Badness. His mercurial magnetism snapped the crowd's attention. At 55, he danced with the effortless cool he always has — the slides, the spins, the latter-day James Brown moves. His voice was supple, and his falsetto positively glowed. His guitar solos were ecstatic expressions of emotion, as eloquent as another voice.

The concert mixed lesser-known pieces with revisionist versions of hits. So you had the old B side "She's Always In My Hair" and "Something in the Water (Does Not Compute)." And you had a "Let's Go Crazy" that was slowed down from its manic original and settled instead into a hypnotic rhythm.

Prince recast other songs in a new light, too ... or in no light at all. For "When Doves Cry," he asked that the lights be turned off, so he sang it in the dark. That "in the dark" is literal; the audience couldn't see him, just hear him.

He clearly doesn't adhere to any rules, so why shouldn't he wrap up his main set with a trio of singles that he co-wrote but wasn't the main artist on — The Time's "The Bird" and "Jungle Love" and Sheila E.'s "Glamorous Life"? And, for the second encore, he let the intro to "Purple Rain" unspool with a lengthy saxophone solo before he even came onstage and then did his own guitar work before finally segueing into singing. He backed off at various moments, letting the crowd sing the lyrics — or sometimes, he'd shout out, "Sing it!" as a cue.

Prince devoted a segment to the musicians he learned from, too — a little Curtis Mayfield, a little Aretha Franklin. Leading into this sequence, he said, "We heard you were starved for the funk up here." Well, he added, starve no longer.

Periodically, Prince, cutting a sharp figure in a butter-colored suit, pulled fans onstage to dance.

At one point, he said of the whole arena, "How many in this club right now? 10,000 in this disco right now? ... This is lovely."

Although he had asked concert-goers to put away their phones, he later told them to get the cells out again to call their neighbors and "tell 'em you're at the coolest place on Earth right now."

For Friday's concert, the opening act was jazz diva Esperanza Spalding, whose expressive voice and performance vitality was on full display.

Prince will perform the last of his trio of Mohegan Sun concerts at 8 tonight, with opening act Janelle Monae. Tickets are $125 and $195. Visit mohegansun.com.

k.dorsey@theday.com