The daxophone, invented by Hans Reichel, is a custom made musical instrument of the friction idiophone category. It consists of a thin wooden blade fixed in a wooden block (often attached to a tripod), which holds one or more contact microphones. Normally, it is played by bowing the free end, but it can also be struck or plucked, which propagates sound in the same way a ruler halfway off a table does. These vibrations then continue to the wooden-block bass, which in turn is amplified by the contact microphone(s) therein. A wide range of voice-like timbres can be produced, depending on the shape of the instrument, the type of wood, where it is bowed, and where along its length it is stopped with a separate block of wood (fretted on one side) called the "dax."
http://en.wikipedia.org/wiki/Daxophone