I definitely think it’s possible to learn piano without a piano teacher. As I said in the beginning of this Q&A, most of what I’m capable of is actually self-taught. I only had a teacher for a few years when I was young. Obviously having a teacher can make a huge difference, but you’re definitely also able to learn piano on your own. Many of my friends have learned piano on their own and actually they play at a very decent level, I think.