We present PianoTouch, a wearable, wireless haptic piano instruction system, composed of (1) five small vibration motors, one for each finger, fitted inside a glove, (2) a Bluetooth module mounted on the glove, and (3) piano music output from a laptop. Users hear the piano music and feel the vibrations indicating which finger is used to play the note. We investigate the system's potential for passive learning, i.e. learning piano playing automatically while engaged in everyday activities. In a preliminary study, four subjects learned two songs initially and then wore the PianoTouch glove for 30 minutes while listening to the songs repeated. One of the songs included tactile sensations and the other did not. The study found that after 30 minutes, the PianoTouch subjects were able to play the song accompanied by tactile sensations better than the non-tactile song. These results suggest the value of a more detailed study.