If the Festival had an audience prize, Borusan Quartet would have won it on their first visit three years ago. They bring us Mozart’s A major Quartet, famous for the Andante’s delicious set of variations, later copied by Beethoven in his A major Quartet, drum taps and all. They follow with Beethoven in electrifying C minor mode where a dark, dramatic opening hurls itself at us before softening to a bright and singing second idea.