After all the celebrations for the 70th anniversary of the Edinburgh International Festival last year (during which it was awarded the EFFE Special Award), the 2018 programme has something of the feel of getting back to normal. It is also Fergus Linehan's fourth year in charge and so can now truly be said to be his own vision. “It's lighter,” he says, after the serious matters of recovering from war addressed during the 70th year, “for a start we have three comic operas.”

Edinburgh in August is such a maelstrom of creative activity that the Director of the International Festival doesn't feel he has to cover everything. With several independent festivals running concurrently, covering literature, film, science, television, military tattoo in the castle – and then the massive free-for-all of the Fringe mopping up just about everything else conceivable – the original festival can focus calmly on classical music, opera, dance and theatre, confident that the rest is taken care of. “Our role in the overall festival ecology,” (how many small cities think of the luxury of a festival ecology?), “is to find the most interesting artists at the top of their powers and put them in the most ideal circumstances we can. We have to create the space for great virtuosity, real seriousness, so that  coming to Edinburgh at festival time is not all about lunch and parties.”

However there has to be a balance between the difficult and good fun. “The festival is not just a beautifully polished piece of mahogany. Even we need to broaden audiences in different ways: a range of theatre, some longer runs, using The Hub,” the converted church used as a general festival home just outside the castle walls, “as a sociable space.”

Over the decades the International Festival has developed internal rhythms of its own, almost insulated from the mayhem in the streets. There are grand concerts in the venerable Usher Hall (built by the owner of a brewery but for most of its history not allowed to serve alcohol on the premises); opera and large scale dance and drama take place in the relatively new Festival Theatre, and every day begins with a late morning concert in the 900 seat Queen's Hall, a delightful 18th century space which is perfect for small ensembles and song.

For me the Queen's Hall concerts have become the most treasured part of the festival over the last forty years – whatever the excitements of the night before, the day starts with two hours of music, immaculately performed to a still and attentive audience. Fergus agrees. “It is quite unlike anywhere else because it happens every morning. These concerts have a very flexible audience, which gives us more freedom than in any other part of the programme. Chamber music is having something of a renaissance in any case but if you end up with six hundred rather than nine hundred listening, it is not the end of the world.”

The guiding principle for Fergus is to ask, “what would we be adding to the mix that Edinburgh doesn't have otherwise.” He cites complete opera productions that are not co-productions, where each house or festival re-stages its own version. “Opera companies these days are not designed to tour but we want to see what they do because it is successful. It adds a level of complexity to the planning but it means it is special.”

So this year there's Rossini's La Cenerentola from the Opera National de Lyon, and the Barber of Seville from Théâtre des Champs-Elysées. Most excitingly the resident company is the Théâtre des Bouffes du Nord, which brings three productions. There is The Beggar's Opera in a period instrument version with musical theatre (rather than operatic) voices and improvising actors, directed by Robert Carson and conducted by William Christie, more usually found in Paris with Les Arts Florissants. Théâtre des Bouffes is the home of the great – not a word I use lightly – director Peter Brook, now ninety-three but going strong, who offers his new exploration of what constitutes justice, The Prisoner, to Edinburgh. In a third collaboration with anglophone directors, Théâtre des Bouffes du Nord brings Katie Mitchell's merger of theatre with live film, La Maladie de la Mort. “Yes, we've ended up with a very French year,” admits Fergus, “but the next one will be very German.”

Perhaps just to prove again that the Edinburgh International Festival is not just that 'polished mahogany', down in the old port area of the city, Leith, the festival has its non-classical Scottish music programme, Light On The Shore, with genres “from punk to post-punk, from new wave to no wave, from alt folk to pop folk, from ambient electronica to techno”. And the main festival starts and ends with two massive outdoor events; a fireworks from the castle evening that's has been the traditional finale since the 1980s, and a more topical and innovative opener – a digital performance outside the Usher Hall celebrating the disparate topics of Scotland's year of young people and the centenary of the end of World War I. “Inspired by themes of communication including telegrams sent by young soldiers in 1918, Aberdeen Standard Investments Opening Event: Five Telegrams weaves a newly commissioned orchestral score, projected digital artworks and live participation together to consider themes of machines and codes, censorship, propaganda and reconciliation.”

With such a mass of activity in the city all at once I wondered whether the International Festival feels hemmed and fighting for venues. “There are times when it feels extremely crowded,” Fergus says, “it's less about  being hemmed in than about whether the Zeitgeist accepts the complexity and seriousness of intent. Edinburgh has to be respectful of the whole festival ecosystem. And there's never a year when the Fringe does badly and we do well. There are areas where we can all do better – in the small and experimental, the new works from other cultures. But the real issue is, this can't be just a party – we have to be sure that our quality, innovation and global reach is not dissipating.”