Long traditions of democracy and meanness have made Britain rather good at the sort of festival that blurs the divide between professional and amateur, participant and listener. It gives everyone a chance. It doesn't cost like Salzburg. And a good example to put beside St Endellion, which I wrote about last week, is Lake District Summer Music: an annual event that merges a temporary academy for young string players with a public platform for distinguished artists who come both to play and teach.

It's a step up from St Endellion in that it doesn't nurture cello-playing bankers. But it decants its better students from the summer school into the festival, providing many with their first paying audience away from college. And as the focus of the whole venture is string quartets (plus other groupings), it provides the audience with day-by-day examples of what it takes for four or so players to develop the collective instinct of true chamber style.

Some players come with established groups, others form ad hoc ensembles. The difference shows. Of those I heard at Ambleside Parish Church, the most promising were the incisively articulate, all-woman Saskia Trio (post- graduates from the Royal Northern College of Music in Manchester) and the racier, more style-conscious Cat Quartet (based at the Royal Academy of Music in London).

But the inevitable stars were the Chilingirian Quartet, who are not students but celebrating their 25th anniversary - albeit with changes of membership. Only the 1st violin and cello have been together from the start, and their playing style has changed since those golden days of Radio 3 when in lunchtime broadcasts from St John's Smith Square Patrica Hughes taught us how to say their name in perfectly-formed English elocution. They sound looser in attack now, not so white-hot in intensity. But they remain giants in their field, and their programme came at strength - with the world premiere of a new quartet (No.3) by the South African composer Peter Klatzow that combined French civility of manner with a new-world openness and boldness of harmonic colour. Not a heavy score, but satisfyingly complete.

Down South, Glyndebourne has revived its Theodora: the hit of last year's season and the only Peter Sellars production whose all-Americanness has ever seemed to me a liberating as opposed to limiting indulgence. From the clean, symbolic imagery of the huge, glass, fractured objets that comprise the set (message delivered: fragile, ancient) to the synchronised semaphore of the chorus movement (purposeful for once,in that it gives visual expression to the counterpoint they sing), this radical response to Handel's oratorio on early Christian martyrdom is supremely stylish.

While the revival brings a new cast, without the magisterial vocal presence of Lorraine Hunt's Irene (star of the show last time) or the elemental purity of David Daniels' Didymus, it has a fine replacement countertenor in Daniel Taylor and a glorious new Theodora, Joan Rodgers, who brings more pathos and substance to the role than the original, Dawn Upshaw. The conductor, Daniel Beckwith, hangs on too much to the tempi, but gets good results. And if only the soldiers' orange overalls didn't make them look so like Camden Council refuse operatives, I'd believe every minute of it.