UNCASVILLE, Conn. — “Please, don’t ever let me be,” David Lee Roth sang during the opening song of last night’s Van Halen concert at the Mohegan Sun Casino. “I always want to be by your side.” Of course, he sang the line from “You Really Got Me” to guitarist Eddie Van Halen, and on the fourth show of the tour that fans have been waiting more than 20 years for, it was more than appropriate.

Last night’s two-hour show was plucked strictly from the Roth years, and it seemed clear, if only in retrospect, that in contrast to the earnestness of the Sammy Hagar years, in which the band was staggering under a stylistic straitjacket of its own making, these were the grooving, swinging, hook-laden songs of a band that was only a few years removed from playing Ohio Players covers — the fast shuffle “Show Your Love,” the breakneck “Romeo Delight” and “Hot for Teacher” (neither of which lost a step last night), the sinuous “Dance the Night Away” and “Little Guitars,” classics such as “Everybody Wants Some!” and “Ain’t Talkin’ ’Bout Love” and more. If the audience last night was experiencing a second childhood, it was just as clear that the band was too.

Roth’s replacement with Hagar was an object lesson in being careful what you wish for. It should have worked — it didn’t.

Roth may have lost some of the athleticism in his trademark spinning kicks, but his persona — a combination of toreador, seen-it-all burlesque queen and judo-period Elvis — once again proved indispensable to the music.

Eddie Van Halen looked like a post-punk G.I. Joe but bounded across the stage with his trademark exuberance, and his guitar solos were, as usual, jaw-dropping. His big solo spotlight was notable for the relative lack of his trademark two-handed tapping, with his volume-knob manipulation (resulting in a sound emulating a string section) most impressive.

Drummer Alex Van Halen, Eddie’s brother and perhaps the only hard-rock drummer whose favorite player was Ringo Starr, hit with authority but a touch and sound that was sweet rather than pummeling.

And bassist Wolfgang Van Halen, Eddie’s teenage son, filled in ably for original four-stringer Michael Anthony. If he doesn’t yet have the fretboard agility of the criminally underrated Anthony, his performance was admirable for a young man in his situation. He hit the trademark crystalline vocal harmonies precisely, and if he couldn’t keep up with his jumping-jack father he wasn’t relegated to the new-guy corner either.

There’s no telling how long this reunion will last — this was supposed to happen before, remember? — and there’s no telling whether the magic will be recaptured if the band starts recording again.

But for now, enjoy what’s there. While nothing might live up to the hype of this show, it’s a reunion to remember.

rmassimo@projo.com