Abstract: The subject grand piano action, in common with all piano actions, comprises driving apparatus comprising the key and wippen levers, drive apparatus comprising the hammer assembly and apparatus interconnecting the two and providing for disengagement and reengagement of the driven with the driving apparatus. In the subject action the interconnecting apparatus comprises the jack, pivoted to the free end of the wippen lever and a repetition spring pivoted at both ends, one end at the free end of the jack, the other on the hammer shank. When the key is played and the free end of the wippen lever rises, a cam on the side of the jack facing away from the wippen lever engages a button mounted on the hammer rail and this engagement forces the end of the jack along a hard felt cam on the hammer knuckle.