"Mozart's opera is full of humanity and tolerance. What would he think today?" For a moment I thought Bernard Foccroulle, artistic director of the Aix Festival, was criticising Martin Kušej's production in his speech of welcome; but no, he was explaining that the Austrian director had chosen to update Die Entführung aus dem Serail to the post-World War One era in an unspecified near-east desert where western attitudes of entitlement fuelled modern cultural and ideological divides.

In the light of recent atrocities in France and Tunisia, he and the director had decided to make two changes to the final staging. He didn't say what these were, but given the production's subversive final image - suggesting offstage slaughter - at least one of them was easy to guess.

Kušej’s recent Idomeneo at the Royal Opera House caused ripples to spread on its rubber-shark-infested surface, but having appreciated that show more than many I was ready to be surprised once more by a visionary director. Instead I ended up feeling jaded, which was not something I'd anticipated. So little actually happens on designer Annette Murschetz's unchanging sand dunes that after a while even the music begins to pall. Osmin and his henchmen skulk about in ISIS-style garb, Pedrillo spends much of Act I buried up to his neck, Selim pops in and out of his Bedouin tent for the odd grab at Konstanze...  and the realistic behaviour of everyone within this pseudo-naturalistic setting is constrained by the fact that Mozart requires them to sing.

"Stop the f*ckng singing!" shouts Pedrillo to Belmonte early on in Kušej and Albert Ostermaier's curious Anglo-German 'adaptation' (a euphemism for 'rewrite') of Bretzner and Stephanie's dialogue. But he's just as bad. The two men and their respective beloveds take an age to slip away from mortal danger at the end of Act II because they have a ten-minute quartet to get through first.

Meanwhile Jérémie Rhorer looks after the musical side with a gentle sway and plenty of lyrical grace. As they'd shown at the previous evening's Alcina,  the Freiburger Barockorchester isn't given to brightness, but what it lacks at the top it more than makes up for in ensemble precision and felicitous phrasing. In Rhorer, Aix has a Mozart conductor of the first rank (as he'd already demonstrated with Le nozze di Figaro at the 2012 festival) and he delivers a reading that's urgent without being over-driven, light on its feet yet never frothy. There's no sand in this French maestro's boots. The only blemishes to his direction were a strange fortepiano continuo that sounded like an intrusive ringtone whenever it cut in, and a distractingly muffled offstage chorus for Mozart's sparkling finale that appeared to be stranded in a backstage cupboard.

David Portillo was the pick of the principals: he sang Pedrillo's "Frisch zum Kampfe!" with great style and a convincing presence. Daniele Behle as Belmonte cut a more stolid figure, like a Lieder singer who's ended up on the wrong stage, but he has an attractive if smallish voice. As for the women, neither Jane Archibald (Konstanze) nor Rachele Gilmore (Blonde) seemed at ease with the production: there was a tension to their acting that only softened when they were able to concentrate on singing, which they both did idiomatically if not with great charisma.

As Selim, the Bedouin leader who's on love with Konstanze, actor Tobias Moretti's character arc seems sketchily drawn. His behaviour suggests uncontrollable passion, as when he flagellates himself with thorns, yet his default attitude towards her is one of calm urbanity punctuated only by the occasional angry outburst. There is more meat in the portrayal of his overseer, Osmin, who is pretty scary in the hands of Franz-Josef Selig even if the profundo notes are only just there. He has to shoulder the lion's share of Kušej’s anti-settlement message - which tends to be laid on with a trowel, as when Blonde tells him "You don't treat a woman that way where I'm from". OK. Got that.

The endless, unchanging desert creates its own ennui. Act II is the toughest: it's played out in ever-darkening gloom until by the end it's practically impossible to make anybody out. As the two-hour mark approached without an interval, the audience's restlessness was palpable. It can't have helped that on Provence's hottest night of the year the spectators were suffering from sympathetic sensory discomfort, with temperatures in the Archevêché still in the high 20s and the witching hour only minutes away. There were more than a few empty seats after the interval, and not because sensitive souls had rushed out clutching their mouths in horror. I fear they fled out of boredom - an indictment that's infinitely more alarming for any director. Tell it not in Gath, or wherever we were supposed to be, but this Entführung is a little dull.