Bemused euphoria hung in the air of the Argyle Works at the end of Mittwoch aus Licht, which has finally received its first staged performances, 15 years after Stockhausen completed it in 1997. Four sold-out performances and at the end of each the audience wanted to stay, to capture a fleeting moment. At least they could buy the t-shirt.

Yes, there are camels and helicopters and musicians on trapezes, all the things that made the opera infamously unstageable, or just infamous. At least now we know it really is stageable, given money, time, intense skill and commitment, all of which were in abundance last week in Birmingham; that it isn’t just another crazy dream bestowed by artists to vex future generations; that it belongs to the seven-part Licht cycle as an uplifting, sometimes transcendentally beautiful instalment of a work that will demand our engagement with it long after this premiere is a distant memory.

Naturally the euphoria arises partly from the sense of enduring and belonging to a unique event – ‘I was there’. But it surely also stems from the nature of the work itself, which makes serenely manifest the composer’s expressed conviction that ‘Wednesday is the Day of Reconciliation’. Like the other parts of Licht, 35 years in the making, Wednesday is the day of many things, ‘spatial phantasms’ among them. Even this apparently gnomic expression opens up after a while, revealing one way of viewing a multi-layered work and also illustrating the uniquely ambitious breadth of Stockhausen’s imagination. A 50-minute long electronic greeting suspends us in weightless darkness, illuminated here and there – all around the audience, in fact, seated as we were on picnic stools in the shell of a former chemical factory – by vignettes of flight and love and the joy of communication itself: a mimed ‘Happy Birthday’; floral-print ladies kissing beneath umbrellas up-turned into satellite dishes; children dancing in the rain.

Having made our way to the other half of the shell, we’re surrounded by delegates of a ‘World Parliament’, who debate the nature of love, high over our heads, in terms of astonishing vocal virtuosity (the singers of Ex Cathedra), like an older, wiser reincarnation of Stimmung, Stockhausen’s 1968 anthem to the blissed-out generation. Higher still rise the level of competition, and the performers, in ‘Orchestral Finalists’, where 13 instrumentalists vie for supremacy above us. Then an even more abstractly formed group of musicians (the Elysian Quartet) takes to the air in the Helicopter String Quartet, whose glissandi and tremolandi hold in a state of nervous tension the musical formulas that animate the rest of the opera.

(Almost) finally we are in space, dazzled by intergalactic light, as we witness the election of an interstellar president, a camel turned radio operator who unlocks the Tower of Babel by translating messages from across the universe. Being least unlike the scene of an opera as conventionally understood, ‘Michaelion’ is also the least easy to encompass for the listeners – to say nothing of the performers, a choir and several instrumentalists who must all perform parts of stratospheric difficulty from memory and with no conductor. A sextet sings lines that Stockhausen would make into his own epitaph: ‘Sing love forever,’ they urge, ‘through conscientious formula music in praise of God.’ They recede from sight and sound. We drift or float back into the other hall, greeted by the electronic seascape from ‘Orchestral Finalists’. It is a magical end.

You don’t, I believe, have to be a Stockhausen cultist, or a specialist, or a Christian or an optimist or anyone in particular, to be swayed, persuaded and finally embraced by the five-hour panoptic tableau of Mittwoch. Masterminded by the director Graham Vick and the musical director Kathinka Pasveer, the production stayed close to the spirit and humour of the score, incorporated the common touches which are a feature of the Birmingham Opera Company, and made the most of specialists who worked with the composer for years before his death in 2007. Further viewing: watch the Helicopter String Quartet and Michaelion (in its Stuttgart premiere).