But he could not ; he had a harp and he often tried to play on it ; but his clumsy fingers only made such discord that his companions laughed at him and mocked him , and called him a madman because he would not give it up , but would rather sit apart by himself , with his arms about his harp , looking up into the sky , while they gathered around their fire and told tales to wile away their long night vigils as they watched their sheep on the hills .