Riddle!

Ok folks, inspired by my friend...from now onwards I shall post riddles for you peepz to try solving them till I ran out of them...

Here goes the first of the series...

A man was walking down the street, when he bumped into his long lost friend.
After the usual how-are-you-i-am-fine bullcrap, the friend asked if the man had any children.

Friend: "Do you have any children?"
Man: "Yes. 3 sons."
Friend: "How old are they?"

Being cheeky, the man refused to tell him outright. So he said...
Man: "If you multiply their ages together, you get 36" (e.g. 9x4x1)
Friend: "Hmm...there are quite a few possibilities."
Man: "If you add their ages together, you get the number of houses opposite the street."

The friend looked across the street, thought for a moment and said...
Friend: "Impossible to tell yet, I need just one more clue."
Man: "Hmm...my eldest son plays the piano."
Friend: "Ahh...I get it now!"

----------------------------------------------------------------

BIG QUESTION: How old are the 3 children? =)

----------------------------------------------------------------

Very Important Assumptions:
1) Age is strictly in years.
2) Eldest son's age is greater than each of the other two sons'.
3) Friend is smart.