Double escapement is a feature of many acoustic and some high end digital pianos that permits a note to be repeated even if the key had not yet returned to its maximum vertical position.
Double escapement permits a note to be repeated even if the key had not yet returned to its maximum vertical position. For acoustic piano, first proposed in 1821 by Sébastien Érard. Digital pianos with three switches/sensors per piano key also allow a repeated note without need to fully lift the key all the way up.
