(Kinda) Unwanted Audience

You've been playing guitar for nearly 4 months now. You have some skill, a few songs, 6 or 7 riffs. It's all good. One summer evening, you left your bedroom window open (Probably because you were being cooked alive). You played one song. At the end of it, you heard applause. From outside. By the time you checked, nobody was there. Next day, same thing. Then it became normal. Applause would be outside of your window every time you completed a riff or song. Then, one day, you heard a girl call out: "Can you play Wonderwall?". So you did. Then, came the song requests. Today, you want to really see who's there...