The New Zealand Symphony Orchestra is on the road with Swedish clarinettist Martin Fröst, one of the world's finest players of the instrument. He'll be playing Mozart's Clarinet Concerto, a work he's been touring world-wide. The orchestra also performs Beethoven's Symphony No. 6 in F major, Pastorale and contemporary composer John Adams' Shaker Loops, to mark the American composer's 70th birthday year. Peter Hoar reviews.