A dog has become an online hit after being filmed playing the piano and singing at the same time.Piano-playing Petu charmed thousands of YouTube users after her Finnish owner uploaded a video.Petu, who stands on her hind legs to reach the piano, can be seen 'playing' the instrument with both paws and - to add some variety - her nose.With her muzzle held high, the dog howls out a tune while wagging her tail enthusiastically.