The Wikipedia article below gives an overview of innovations in piano, highlighting 19th century developments and later contributions that sought to improve an already mature piano-making technology. What do you guys think? I thought an aspect missing in the article was features that allows for softer sound: una corda in grand pianos, felt and sordino pedals in upright pianos (which are emulated by Steingraeber in their concert grand). But the most interesting thing seems to be the part about the magnet-adjustable variable touch system.