You nock on the door.
You hear an old voice ask "Who is it? Who ever it is, you better have a good reason for desturbing me at this hour!" You introduce yourself and why you knocked. The door slowly slides open, and you see an old man standing in the doorway. He greets you with a smile, and tells you that if you want to hear more, to "come on in", if not, please leave so that he can get back to his music.