By the 1820s, the center of innovation had shifted to Paris, where the Ãrard firm manufactured pianos used by Frédéric Chopin and Franz Liszt. In 1821, Sébastien Ãrard invented the double escapement action, which permitted a note to be repeated even if the key had not yet risen to its maximum vertical position. This facilitated rapid playing. When the invention became public, as revised by Henri Herz, the double escapement action gradually became standard in grand pianos, and is still incorporated into all grand pianos currently produced.
One noticeable advantage that the grand piano action has over the vertical action is that all grand pianos have a special repetition lever in the playing action that is absent in all verticals. This repetition lever, a separate one for every key, catches the hammer close to the strings as long as the keys are played repeatedly and fairly quickly. In this position, with the hammer resting on the lever, a pianist can play repeated notes, staccato, and trills with much more speed and control than is possible on a vertical piano.
