is that possable? my choir teacher's piano wont play a D. he said thats b/c it broke... is that possable?

thanks!

I am doing Grade 7 at the moment and my teacher always tells me I play to loud. My Grade 5 examiner also took away 5 marks in one of my pieces for the same reason.Then a few days ago a string broke on my piano but I was able to get it fixed the day after so it was no big deal!