A Brief History of Piano Action Mechanisms

Abstract

The action mechanism of keyboard musical instruments with strings, such as pianos, transforms the motion of a depressed key into hammer swing or jack lift, which generates sound by striking the string of the instrument. The mechanical design of the key action influences many characteristics of the musi cal instrument, such as keyboard responsiveness, heaviness, or lightness, which are critical playability parameters that can “make or break” an instrument for a pianist. Furthermore, the color of the sound, as well as its volume, given by the shape and amplitude of the sound wave respectively, are both influenced by the key action. The importance of these mechanisms is highlighted by centuries of studies and efforts to improve them, from the simple rigid lever mechanism of 14 th -century clavichords to the modern key action that can be found in concert grand pianos, with dozens of bodies and compliant ele ments. This paper presents a brief history of this evolution with a focus of mechanism design and development, with an analysis of the most important designs from a technical perspective. Four milestones can be identified in the history of the key action mechanism: the clavichord, the harpsichord, the fortepiano, and the modern piano (including both the grand and upright pianos). In ad dition, modern electro-mechanical, analogue, and digital instruments are briefly introduced to identify the current trends and discuss possible future devel opments of key actions.