My neighbour has a piano on the party wall. I raised the issue with him some months ago and since then this has reduced, however as agreed he does still play for a little while every day. Our house is now on the market and we've got a couple (not as many as I would like) of viewings booked in. Would it be reasonable to ask him not to play when we have viewers. I wouldn't want them to think it's constant when it isn't but if he happens to be playing for the 10 minutes you're viewing, I think I'd assume it was a regular thing.