They taught us because they wanted to pass the knowledge on and educate young musicians. It was not because they had to teach because they failed as musicians. There is a huge difference in the reasons why someone is teaching and what they can offer and what they cannot offer.
New York City is home to so many people from so many places and the uniqueness of it is that you never feel a foreigner. English is almost hardly ever heard in the subway. In fact it's weird.
