Did it take a curtain to prove Kraftwerk are human after all?
As the four self-styled 'mensch maschinen' embark on their encore at Sheffield City Hall after a stunning set, there's a hitch.
One of the huge black drapes in front of the stage is stuck fast, requiring a strong technician to hoist it open for a full 15 minutes to prevent the group from being unceremoniously shrouded.
On the scale of emotions, the quartet just about reach 'mildly ruffled'.
But given Kraftwerk's forbidding reputation, that's something.
German electronic pioneers from Düsseldorf who pointed the way to all kinds of musical futures in the 1970s - synthpop, techno, house - they're back in Sheffield for the first time in 26 years on their first full UK tour in well over a decade.
The sell-out dates are a continuation of their 3D shows that have drawn acclaim at museums, galleries and festivals around the world; audiences are handed special glasses and treated to seamless two-hour concerts exploring Kraftwerk's catalogue.
The favourites are all here - Computer Love, The Model, Autobahn, Tour de France - in loud, crystal clear audio (their engineers spend an age rigging up each venue, by all accounts), accompanied by fittingly retro-futuristic visuals, from vintage cars to ancient-looking computer devices, zooming out of a large screen.
Sole remaining founding member Ralf Hütter and three more recent recruits - Henning Schmitz, Fritz Hilpert and Falk Grieffenhagen - wear form fitting, grid-patterned black neoprene suits, and very much appear to be playing most of the music live, despite the clear temptation to rely on a backing track.
Some numbers are updated and reshaped - an opening suite of songs from Computer World is given a 2017 sheen - but others sound much as they did. During a note-perfect Spacelab the screen shows a UFO landing outside the City Hall. The graphics are perhaps deliberately primitive, but it's a nice touch.
What stands out most is the classic melodies, and their sheer number - Neon Lights, from 1978's Man Machine album, is a genuinely touching song, all shimmering keyboards and awestruck lyrics hymning a city 'made of lights' after hours.
There's also something especially pertinent about seeing the band present their forward-thinking, overwhelmingly European worldview to a city that voted for Brexit.
One would think, given the gulf in time since their last visit, Sheffield may well never see Kraftwerk again.
But an encore of The Robots is delivered by their famous automaton doubles - four unsettling, moving mannequins.
So who wouldn't bet against an infinite regeneration? Musique Non Stop, as their closing song recommends.