Can a set of show tunes and Great American Songbook standards, rendered with a healthy measure of respect and virtuosity, also be a punk-rock show? Or at least something that kinda/ sorta feels like one?

Disney/Randy Holmes

That basic question arose over the course of seeing Lady Gaga’s secret post-midnight performance at downtown L.A.’s movie-palace-turned-music-club, the Belasco. There are surely a few performers out there who have a feel for both the classics of the Broadway/movie-musical era and raw-power rock ‘n’ roll. They just don’t exist at anywhere near the superstar level, and even in a more niche world, they probably know better than to try to combine these extremely different ethos. Lady Gaga, thankfully, does not know any better. After catching Monday night’s show, I’m happy to report that she is the woman who can marry the controlled genius of Tin Pan Alley and the wildly performative id of punk’s chaotic spirit… if only for one extremely memorable late night (or early morning).

The show had her and a truly crackerjack six-piece band barreling through her new “Harlequin” album in its entirety, with the energy level turned up to 111, well beyond any recorded versions. No one should imagine that she will stay in this mode for very long (she already characterized the current record as “LG 6.5,” with a straight modern-pop album 7.0 to follow in four months). She’ll probably never even do another gig like this, with or without the strange set dressing at the Belasco that further pinned this as a unique moment in time. But as a one-off, it was glorious. I’ve been on record as being high on Gaga shows in the past, including her Dodger Stadium gig, her Enigma residency and, especially, her Jazz & Piano shows in Las Vegas — to which the “Harlequin” stuff bears at least superficially a black-sheep-cousin relation. Having seen all those, I’m here to tell you her Belasco performance was utterly bonkers but also one of the best things she’s ever done.

I’d say you had to be there to get it, with the cone of silence that was placed over the show, including the pouching of phones and watches and no photography released. (The photos seen accompaying this piece are from her Kimmel performance the following night.) But perhaps you didn’t have to be, assuming the cameras and cranes and waivers to be signed assured that there is some intended release, yet to be announced. Maybe it won’t transfer to whatever screens it ends up on; maybe you’ll be looking back on this when you see it in two weeks or six weeks or a year and thinking: What was he on about? That’s the risk in raving about something destined to be seen sooner or later on a small screen. But in the room, at least, it felt as galvanizing as, say, the tour-ending show Jack White did in the same venue a couple of years ago. Which is not something I walked in expecting to say about a show that was destined to have “That’s Entertainment,” “That’s Life” and “Get Happy” on the setlist.

Exactly what the show was meant to convey, on a psychological level, remained a little bit mysterious, and even unsettled, in a good way. The production design for the set couldn’t have been more striking, or further away from any show-biz norm. The stage was dressed up as a dimly lit, disheveled studio apartment that has seen better days — and whose inhabitant probably has, too. Light peeked in a window through throughly messed-up venetian blinds that looked to have never been repaired from damage suffered in some rage or raucous party. Gaga’s “bed,” which she occasionally jumped up and down on like an unrestrained child, consisted of unmade sheets strewn across a mattress laid out on the floor — and a pillow that the singer gleefully ripped to shreds, finally showering the audience with feathers that flew all the way up into the balcony.

Was this set supposed to be the humble lair of Gaga’s not-quite-on-her-rocker character from “Joker: Folie à Deux”? This would be a reasonable interpretation, for an audience that hadn’t yet seen the movie, whose premiere the star had attended hours earlier. And certainly she danced her way through the show like a possible madwoman, or someone hopped up on coke. But actual insanity probably wasn’t exactly the idea. At one point in the show, Gaga stopped to talk to the audience about how this was about her getting back in touch with the unbridled joy someone might experience in music and in performance before the expectations of a career knock that out of ‘em. So maybe the messy apartment set was just meant to reflect the mindset of somebody who is just so completely focused on finding manic ecstasy through art that little things like housekeeping and home repair take a back seat. And maybe we’re rethinking it either way — but the design certainly added a level of irony and intrigue that wouldn’t have been there if she’d just been performing “If My Friends Could See Me Now” in front of a stock phalanx of bright lights.

But in front of this ambiguous backdrop was the unambiguous sight, and sound, of Gaga seeming to have the manic time of her life. Anyone who’d heard a report that she was not unduly high-energy at the film premiere a few hours earlier had to laugh at how she seemed to be consuming a whole year’s worth of energy in one hour-and-a-half-or-so performance. (With smartphones locked up, it was difficult to know when the show actually started or how long it lasted, with about half of the songs getting a do-over — with no flagging effect on her pep or the audience’s deafening enthusiasm levels.)

Gaga had a small rag doll she occasionally picked up off the mattress and used as a performing partner, and she treated herself with all the spontaneous malleability of a floppy effigy — combined with the lapses into sheer precision you expect out of somebody who’s been training as hard as she has all her life. Befitting the advanced age of some of the material she was performing, there were some flapper-style moves, when Gaga wasn’t transforming herself into a one-woman moshpit.

If it felt like the show had a legit punk sensibility at times, that was only in the set dressing, energy and the star’s enjoyably unhinged performance style, not anything you’d hear in an audio-only soundtrack. There, her singing was as flawless as ever, despite her seeming to work off a week’s worth of calories with every number that proceeded. The phenomenally good band very much had a rock ‘n’ roll spirit, although stylistically only a few of the numbers fit directly into that vein. With both a trumpet and sax player in constant motion in the mix, the group often slid into New Orleans-style jazz — most obviously when they did “Oh, When the Saints,” in a rendering that did Louis Armstrong proud but also made it feel like Armstrong had always been a rocker.

The show had instrumental interludes, presumably for costume changes — although each time Gaga reappeared, it was in a different outfit that was mundane by her standards, with glitz never threatening to intervene. The concert opened with the surreal appearance of a spookily lit barbershop quartet, who reappeared later to be accompanied by the band in singing “Love Will Tear Us Apart.” One of the interludes had the group playing a tremolo-guitar-filled instrumental that was identified on the setlist (which Gaga herself leaked on Instagram) as a Cramps song. It was that kind of night: rooted in the best that mid-century Broadway and movie musicals had to offer, but  suitably genre-inspecific and weird around the edges.

That’s why I give this show a slight edge over her Jazz & Piano residency in Vegas, which I liked quite a lot. Gaga was certainly able to make the nostalgia evident in that show into something… well, Gaga-esque, but there was undeniably an element of cosplay in stepping into the costumes and songs of another era. The catalog she is dipping into for her “Harlequin” era is similarly throwback, obviously — despite the presence of a bit of original songwriting, and selections from lesser-known, slightly more contemporary shows like “The Roar of the Greasepaint, the Smell of the Crowd.” (That’s where the song “The Joker” is derived from, though most people guessed it was a fresh original at first.) But it’s a real kick to see her roughly returning to America’s shared past of show tunes and taking greater liberties, making the vibe very much her own. You’d never doubt the reverence she has for these songs, but there’s liberation in her being able to treat them kind of like that unmade bed.

This studio-apartment set had room for a grand piano, and Gaga calmed herself down enough to sit at it for a spell, singing first a solo rendition of her current hit with Bruno Mars, “Die With a Smile,” and then use that as a segue into (naturally) Charlie Chaplin’s “Smile.” This was more the elegant Gaga that the establishment has come to know and love — a Lady fit for a sophisticated concert hall. That was, literally, grand, but the best parts of the show came in seeing her turn into the rocker she’s always threatened to be… to the point of picking up an electric guitar during “Happy Mistake.”

Her motivations for doing an album beyond the “Joker” soundtrack album aren’t entirely simple to suss, but the best possible explanation is that, having proven she’s a good collaborator, she wanted to do something that was purely her vision. If so, this further culmination of the project, as a filmed show, confirms her unfiltered take can be not just interesting in a conceptual realm but a real, visceral kick in the pants. And if this single performance is as close as she ever comes to doing a pure rock album or tour, it’d be enough. For those of us who love old-school Broadway, furious bands, and a singer who has what it takes to do any of these styles, who could ask for anything more than a “World on a String” that slams?