first a song is played for him , then he plays for them ; the last one to run out of song will be the one to win ; the prize is known by many bards , but few have ever won ; it is a silver , magic harp that never loses tone ; the centaurs charge a healthy sum from every challenger , but if the bard should be the one to sing with greater splendor ; he may keep the magic harp and use it as his own , but when he dies it is returned , since it is but a loan .