We describe an apparatus that will sense the vibration of a wineglass through the jitter induced on a laser beam reflected from the glass wall. A positive feedback system provides a high level sound-wave-train that maintains the vibration of the glass, while a light-emitting diode lighting panel, also deriving its signal from the feedback system, allows the motion of the glass to be clearly observed in a user-controllable way. The positive feedback signal, along with observations from some additional experiments, can be used to highlight some of the nonlinear aspects of the resonance. Although the apparatus is primarily intended as a demonstration exhibit, we have found it useful also as a physics teaching aid.