Explain a sound that's coming into a room. Introduce it like it is a person.
I heard the bass first, like thundering footsteps, drawing nearer. The door to the hallway was open, so I rose to close it, but as I drew near, I heard the first high notes, like whistling. A cheery tune to a menacing step. But even as I shut the door, the chorus slipped through and filled the space. It was here now. I should have known better than to study near the band room.