My first impression of the famous opera-centric festival that takes place in Aix-en-Provence every year is not the impression I had expected. Because, living in the outside world, away from its mazey streets, Aix appears to mean big names, spectacular productions and largely core repertoire. That's what gets the attention, anyway. Perhaps because that's largely what gets issued on DVD. Yet my first experience was of a classroom. A real classroom, complete with benches and long tables with place numbers on white stickers (and old-school classroom vandals, as the aged lady to my left surreptitiously peeled her sticker away from its place whenever she thought nobody was looking). It was a masterclass given by the composer and IRCAM graduate Raphael Cendo.

Everyone was very serious. I was 10 minutes late and had to negotiate with the ladies on the door who were shocked that I would consider entering late (something I would never do, at least not mid-work, for a concert, but for a masterclass it's pretty common). Then I was guided along the path and shown where to walk so that my feet didn't make a noise on the gravel. I entered the classroom terrified that my sitting on the bench might provoke an errant groan of the wood. The whole thing felt as though I were at a beetle-browed contemporary music academy. I half expected the young Pierre Boulez to leap out and yell at me for my lateness.

And yet Cendo proved a disarming host. His music is very much what newcomers to the style might term the scratch-and-saw variety (I now await a pained phone call from Gramophone's learned contemporary music reviewer Philip Clark) but he explained with passion and clarity his vision – the way he seeks to move past boundaries to suggest what might lie beyond, to constantly ask philosophical questions and how this kind of exploration has been a constant in classical music, in all art in fact, since its earliest days. The concentration of the spectators, the smiling intensity of their lecturer and the virtuosity of the resident string quartet paid off. It was all rather riveting.

So how does this kind of activity sit with the more traditional fare for which Aix is famed? In his office overlooking the great Théatre de l'Archevêché, the festival's director Bernard Foccroulle clues me in. "We are here to give life to opera and music, to balance its past and its present. But because the weight of the past is so heavy it could crush us, we have to be creative to keep that balance." And so his programming starts with the here and now, as he gathers together key creative personalities for future productions. They meet in Aix, they discuss their projects and very often even the casting has been agreed before the rest of the preparation starts in earnest. Foccroulle is concerned with nothing less than reinventing opera with every show. This season, for instance, he has brought the artist William Kentridge to direct Shostakovich's The Nose and the Japanese choreographer Saburo Teshigawara to mastermind a staging of Handel's Acis and Galatea. "People say to me, 'How did you get the dancers to sing so well?'" chuckles Foccroulle. "They're all singers! But if we're creating that kind of confusion, we're on the right track."

Later, the director of the youth academy here, Emilie Delorme, points out the wealth of activities aside from opera at Aix – "The festival has changed over the years. Now we have composers, we have string quartets, we have many things." But like Foccroulle, she is also focussed on the matching of person to project. "With this season's series of masterclasses and concerts with living composers I had to fight to get the young string quartets we wanted to learn this music! But one of the quartets liked their work so much they have scheduled it for a concert in Paris. That is a huge victory for me, because through our activities they found a piece that perfectly fitted them as artists."

In the evening I experienced more traditional Aix in its great open-air courtyard theatre. Truth to tell, David McVicar's functional staging of Mozart's La clemenza di Tito is not one of his most insightful (and, perhaps a nod to the Aix philosophy of pushing boundaries, he gave Tito a rather irritating set of prancing guards). But the casting was mostly strong, led by Carmen Giannattasio's lustrous Vitellia and Sarah Connolly's Sesto, a model of style and passion. Anna Stephany, a past graduate of the Academy here, was a ripe-voiced, tender Annio and Amel Brahim-Djelloul served notice of great things to come as Servilia. Sadly the announced John Mark Ainsley was replaced as Tito by Gregory Kunde, who by this point in his career should really have moved on to character roles. Yet despite a tenor that has largely dried out, he rose to Tito's closing scenes with fervour and something approaching grace. In the pit, Sir Colin Davis and the London Symphony Orchestra (newly resident here) found character in abundance. Although notably slower than on his old recording of this work, it never sounded it. And his appetite for this music never dims. At a couple of points, the warm evening mistral wind itself seemed to be humming the tunes. Until I realised it wasn't the wind at all. It was Sir Colin. More from Aix – and a report on Natalie Dessay's first European Violetta – tomorrow. 

[This has been updated from an earlier version.]