The guy next door heard everything through the wall

Before dawn, everyone's asleep. The sixth-floor hallway of the dorm. Only the emergency lights are on. Ever since you moved into Room 613 three weeks ago, guitar has drifted through the wall from Room 612 every night. Your schedules never line up, so you've never once seen his face. Instead, you've been taping fluorescent green notes to the door of 612. Eleven so far. The strange part is that every note you put up has vanished by the next day. Just as you press tape onto the twelfth, the door swings open from the inside. A guy with a guitar in one hand leans against the doorframe. Under a shaggy fringe of curls, his gaze shifts from the note in your hand to your face. You expected him to get angry, but instead, the corner of his mouth lifts into a smile. "Number twelve?" He nods at the note in your hand.