Rufus Wainwright bounds out, post-intermission, this time decked out in a red sequin tailcoat with matching belt and slippers.

“And now for something completely different,” he grins. “Yes, you’re all on acid.”

That would explain the time-travelling – here we are at Judy Garland’s legendary 1961 Carnegie Hall concert, barely an hour-and-a-half after Wainwright’s first appearance “dressed like a composer” to introduce his 19th-century-style opera set in France on Bastille Day, 1971.

Cut down to selected highlights of both to fit within the nearly three-hour running time, this incongruous and indulgent Adelaide festival double-header of Prima Donna and Rufus Does Judy is a busy mishmash of ideas carried by some tenacious talent – including, of course, that of Wainwright himself.

An odd pairing of high art and high camp, the two acts differ markedly in tone and style, united only by the refusal of their respective divas – one imagined, one real – to fade quietly into the night.

The imagined is Wainwright’s creation Régine Saint Laurent, a French opera singer making a last-ditch bid to resurrect her career. Jacqueline Dark in the lead role delivers a captivating performance bristling with vocal and emotional range, perhaps drawing from her own circumstances following Opera Australia’s controversial decision last month to drop the popular mezzo soprano from Wagner’s Parsifal.

Laurent grapples with artistic mortality and her mistaking the starstruck fanboydom of young journalist Andre Letourneur (Andrew Goodwin) for romantic interest but, even in the bite-sized version, the plot drags somewhat, exacerbated by the enforced stagnation of the “symphonic visual concert” format that saw the opera singers mostly rooted in place in front of a distraction of a film by Italian director Francesco Vezzoli.

Appropriately for an opera about a woman struggling to cope with losing her voice, the performers all periodically lose theirs, drowned out at climatic moments by an in-form Adelaide Symphony Orchestra (ASO).

Wainwright, who reportedly once joked about his choice to debut the opera in Manchester as he thought it would be safer “somewhere small so that, if it’s a complete failure, nobody knows about it”, perhaps had the same in mind about opting for South Australia to try out a condensed version of the poorly received original – or perhaps he just knew of the talent that would be at his disposal here.

The most prominent example was local pianist Mark Ferguson, artfully setting the tone for Wainwright’s return to the stage as the one and only Judy Garland, impersonated so devotedly he even garbled the exact same lines she messed up back in 1961.

Where Laurent’s comeback bid emerged from Wainwright’s imagination, Garland’s was all too real – the singer and actress bouncing back from alcohol and drug addiction to return to Carnegie Hall in a performance that sealed her place as one of the all-time greats.

From the eyes-rolled-to-back-of-his-head crescendo of Come Rain, Come Shine to his rich crooning of Over the Rainbow, Wainwright offered up plenty of highlights, even if his cool voice felt a little wedged into Garland’s world – one of the most celebrated concerts in music history is a tough act to follow, after all.

He was also a touch casual, cutting off the ASO in full-swing because it had slipped his mind that he wanted to thank all the performers, only to struggle to wrap his lips around the names of “dear friends” and having to ask for the identity of conductor Guy Simpson, who he had also initially forgotten needed introducing at the start of the evening. A less charismatic presence might have been undone by all this but it only added to the wink-and-a-nod boastful schtick of the self-billed “world’s greatest entertainer”.

Of course, why wouldn’t the audience have enjoyed themselves, zonked out as they were on Wainwright’s acid. By no means a bad trip, even if the dealer was holding out on his very best gear.