Listen to the clip below, and I bet you’ll find it oddly mesmerizing.  The Music is “Sugar Plum Fairy” by Tchaikovsky and it’s being played on the “glass harp”, an instrument played by running moistened or chalked fingers around the rim of glasses.  Each glass is tuned to a different pitch , either by grinding the glass to a specified pitch, or by filling the glass with water until the desired pitch is reached.   Close your eyes and listen.   It sounds like you’re listening to a quartet.  Well you are….a quartet of hands.