Its origin is clouded in history, but the juice harp -- the tiny one-stringed instrument that's held against the teeth and plucked -- turns up in similar guises in ancient cultures around the globe. (A 1,000-year-old iron model was discovered in Japan a few years ago.) The name alone is a matter of conjecture, deriving as it does from "gewgaw" and "Jew's harp" to today's less inflammatory moniker. In Germany it's a maultrommel, in Italy a scacciapensieri, and at Lark in the Morning, a marvelously eclectic instrument shop in the Cannery, they call it a jaw harp. Several models are available from all over: domestic stainless-steel harps in every key of the scale; bamboo harps from Asia (including a deluxe model favored by the Maranau tribe); brass harps from Vietnam and the Philippines; even a clackamore, a cross between a juice harp and a spoon, rendered in hardwood. Lark in the Morning carries lots of other (equally worldly) instruments as well -- bagpipes, samba whistles, steel drums, Irish harps, you name it. Just be careful how you play your brand-new gewgaw/jaw harp/juice harp: The great 19th-century virtuoso Karl Eulenstein lost most of his front teeth in the service of his art.