We are sitting in the Flowering Tearoom at the Künstlerhaus in Vienna, on the other side of a room dominated by the mud sculptures of an Ethiopian artist, Elias Sime. Not just mud, I suspect by the smell; dung, also.

Peter Sellars leans toward the tea cups. “These little biscuits you are eating,” he says, almost whispering, “they were made by former prostitutes. They freed themselves and have now formed a bakery. Isn’t it wild? And this Flowering Tearoom is a project of homeless women in Vienna. Those are homeless men running that tea stand. Everything you see here has a story, which I love.” His eyes are twinkling.

Sellars is the most famous agent provocateur in theatre and opera, the director you either hate or adore. When he mentions his 1990 Glyndebourne production of The Magic Flute– the one featuring drug addicts and crazies stalking the detritus of a Los Angeles freeway – he almost grins. “The most hated production in the history of British opera,” he recalls.

But there’s nothing to hate about his childlike enthusiasm and his pleasure in explaining his latest Mozart jamboree, the multimedia arts festival New Crowned Hope, created last year for Vienna, the city where Mozart died, for the 250th anniversary of the composer’s birth. A compact version, spread over five weeks, will run from Wednesday at the Barbican, which co-commissioned several events.

So where is Mozart in this festival? His music certainly takes no starring role. You’ll hear it only in the Barbican’s opening splash, Mozart Dances, showcasing the dance interpretations of the Mark Morris Dance Group, and live performances of two piano concertos and a sonata, featuring Emanuel Ax. Elsewhere, you must seek Mozart through his spirit – a spirit embodied in ways that can appear rather tangential. The Kronos Quartet are coming with the British premiere of Górecki’s lengthy third string quartet. There’s a new John Adams opera; the Malian singer Rokia Traoré; Dawn Upshaw performing an oratorio memorialising the philosopher Simone Weil; a Bill Viola video installation; and six commissioned feature films.

Sellars explains: “After the 250th anniversary overload it’s a joy not to programme his music. I think Mozart himself is relieved. I’m trying to meet him at the point of content, not prettily decorated performances. I’m taking the themes of the works of his last year, The Magic Flute, La Clemenza di Tito, the Requiem, and asking: where can we go from here? How can we carry his thinking about violence and injustice, reconciliation, regeneration and hope, into the 21st century?”

The proof for Mozart’s politically rebellious spirit, he says, lies in the music. Slavery is summoned in words and deed in the operas; Mozart, of course, was for its abolition. The opera Don Giovanni, in Sellars’s view, is “the soundtrack for the French Revolution”. Even the Viennese classical music style, he says, champions human rights by placing the focus on dialogue and free expression.

New Crowned Hope, named after Mozart’s Masonic Lodge in Vienna, includes some exciting work generated by Sellars. At its Vienna premiere, an opera by John Adams, A Flowering Tree, based on Indian folk sources, had exotic, lyrical beauty.

The film component has already proved particularly successful. There’s Apichatpong Weerasethakul’s Syndromes and a Century, in which the Thai director plays magic games with the early lives of his parents, two young doctors in a hospital. Then there’s Opera Java, from Indonesia, featuring gamelan musicians and Javanese dancers. And Sellars’s reconciliation theme – authentically Mozartian, this – is powerfully reflected in Maha-mat-Saleh Haroun’s Dry Season, a compelling two-character drama about violence and revenge, filmed in Chad.

Not one of the films, I remind Sellars, comes from Europe, Mozart’s home. “Quite right, too. There are First World people at the festival. But I just didn’t want to exaggerate their presence. What’s interesting is that the language of film shifts when it’s in the hands of an indigenous person. And we need films from so-called crisis zones, which people see every day on television. But those TV images are without depth, seen through the eyes of a Western reporter who’s flown in for the day in his flak jacket, then flies home.”

The New Crowned Hope festival is the way it is because Sellars is open to every thought, and from all disciplines. “I wanted to make a festival that had film, architecture and food.” We observe again the biscuits – my first made by an ex-prostitute. “The first you know of,” Sellars says, his child’s grin bigger than ever.

— Barbican, London EC2 (0845 1207594), from July 4 to Aug 12

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