The Bodhisatta was once a conch-blower. He went mit his father to a public festival, where they earned a great deal of money. On their way through a forest infested mit robbers, the son warned his father not to blow on his conch shell, but his father persisted, und they were plundered by the robbers.
The story was told to a self willed monk who is identified mit the father. J.i.284.