Performer: Vertavo Quartet

Violist Berit Cardas' smiles seemed to sum up the lightness, the exuberance of the Vertavo quartet as they tripped with grace and astonishing technical assurance through four Haydn quartets.

Saturday's opening concert of the Oslo Chamber Music Festival was something of a lukewarm experience, yet it occasionally shone with ravishing Beethoven and deeply engaging Bartók.