From Craig in Australia:

One day back in the 1980's my parents and I went round to some of their friends house for lunch. My parents knew that I'd be oh so thrilled at the prospect of spending 3 hours sitting round listening to grownups talk so they sat me in the front room of their house that had a tv and this piano against the wall opposite the door. 

For the next couple of hours I sat in that room by myself watching tv and channel surfing. Nothing out of the ordinary happened. I ended up watching some war movie and the last image I remember seeing was some decaying body (great thing for a 6 year old I'm sure). Guess that must have been what made me leave the room to find my parents and I began to high tail it. 

Just I was walking out of the room the piano on the opposite wall began playing all by itself. I looked around by there was no one to be seen. Now this was a pretty old piano, nothing like a baby grand and definitely not one that can play by itself. I listened to the piano for about 5 seconds before I ran down the hallway. 

When I found my parents (at the very back of the house) I told them what had just happened. I finally managed to get them to follow me back to the front room to show them what had happened. Unfortunately the piano had stopped playing by that time. I tried desperately to convince them and then my mum stuck her head against the wall that the piano was on. She said she could hear a faint piano being played but that it was probably by the next door neighbours. The explanation has never sat right with me for the simple fact that the piano music was very loud and very clear, it wasn't muffled or muted as you'd expect when you hear a sound through a wall. 

Needless to say, I didn't set foot in that room for the rest of my time in that house.