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. The cams on the jack and hammer knuckle are contoured such that the jack end and the jack actuation button remain in contact or close proximity to their respective cams throughout engagement and dis-engagement of the jack. There are two mechanical adjustments and one spring adjustment in the action. This configuration enables a simpler, quieter, easier to adjust action which stays in adjustment for longer periods of playing time and with no sacrifice in performance.