Harpsichords and old fortepianos used the single escape mecanism (almost intact since Cristofori invented the piano key mechanism). In the beggining of the 19th century the double escape mecanism was invented by Erard. Basically, this permited you to press the key again without it having to go all the way up because the hammer didnt need to go all the way down necesarilly. Not everyone was happy with this mechanism, and Chopin hated it. Hence, people like Horowitz would say that Chopin is impossible to play as it should be played on modern pianos (I dont agree with this, just quoting). But it was VERY good for technique, because now you could have a lot more control of dinamics and play a lot faster and play repeated notes a lot faster. Now, you can check on any modern piano, the key has a very slight stop on the second escape, when you press the key all the way down really slowly youll feel it. Single escape keys have VERY light action, and you can press the key slightly and it will still sound. Im aware of the incredible advantages double escape mecanism has given the piano, but I really wish there were a way to recreate the single escape feel completely. Its a whole other feeling.
Topic: Double escape mecanism... a mistake?