Just a music box

I have a music box shaped like a piano. It belonged to my grandmother. My mother was also a great lover of music boxes. She died in 2004. Something odd happened last night and I have no explanation. The music box sits on the top of a highboy chest of drawers that was in my parent's home and once belonged to my grandmother. I brought the dresser and chest back to my home when my father died last year. I was reading in bed last night, when the music box began to play. Not like it was wound up fully. Just a half dozen notes and then it went silent. How do you explain that? It hasn't been wound in years. I can't remember the last time I wound it up. I just stared at it as it fell silent. It made me miss my parents all the more.