I thoroughly enjoyed this video of NYU professor Eduardus Halim whom studied with Horowitz discussing about piano playing, practice and many more. I thought I would share this for those that haven't seen it. I particularly enjoyed his admiration for the importance of piano technician as an artistry in itself and how Horowitz was able to achieve his particular sound even with a different piano.
https://www.youtube.com/watch?v=vPQegM7BnUg