The Whispering Mountain: Joan Aiken

In The Whispering Mountain by Joan Aiken, the small town of Pennygaff, the legendary Harp of Teirtu is found - and lost again. For young Owen Hughes and his friend Arabis, it is the start of a hair-raising race to save the harp from sinister Lord Malyn. As they struggle to keep it out of his hands, they are plunged into a wild adventure involving murder, kidnapping, underground worlds, savage beasts, floods, avalanche, the mysterious children of the Pit - and above all, a man who will stop at nothing to get the harp back again.
Winner of the 1969 Guardian Fiction Award.