Oh dear, that sounds absolutely dreadful. I am unfortunate enough to work in a music shop, and occasionally have to put up with this from customers. The ones that do it tend to give you this look, kind of a "hey aren't I great?!" type of thing. I expect this was kind of like that in reverse. 90% of the people that come in are sound, but sadly there is a notable minority who are little more than insufferable tools who happen to be immensely impressed by themselves and think that you will be too. The truly talented people,IME, tend to be the most humble. We see a lot of musicians from day to day, some of them truly outstanding. This young lad came in the other day to buy a cheap digital piano - his playing was so good that I thought he was a professional concert pianist. When I asked him if he was a professional player he blushed and said that he only played by ear, having learnt to play on his Auntie's old upright. I can honestly say that none of us would ever dream of doing this in front of a customer (I'm not good enough anyway!). Why would you even think that was a good thing to do? If we employed someone and they did that, they would be shown the door.