The behavior of the highly dynamic mechanical transmission between the key and the strings of pianos remains insufficiently understood. Called action, this mechanism is essential for the instrument playability and touch. Upright and grand piano actions, although based on similar principles, present quite different behaviors. This work outlines two models, one for each action, that have been carried out using a similar multibody approach with equivalent modeling hypotheses. The models take all the moving bodies into account as well as the intermittent contacts geometry and specific force laws. In addition, experimental validation with high-speed camera have been successfully achieved. Simulations of the models allow, among others, to estimate the maximal playing frequency, to discover the bridle strap and butt spring usefulness in the upright piano, to illustrate the fast repetition capability at a halfway keystroke in the grand piano action and to virtually adjust its settings. These results help in understanding the actions functioning and capabilities, and should contribute to a useful tool for piano makers, showing the interest of the multibody modeling approach for demystifying piano actions behavior and performances.

琴键和钢琴琴弦之间的高动态机械传递的行为仍知之甚少。这种机制称为动作，对于乐器的演奏性和触感至关重要。立式钢琴演奏和三角钢琴演奏虽然基于相似的原理，但表现出截然不同的行为。这项工作概述了两个模型，每个动作一个，使用相似的多体方法和等效的模型假设进行了建模。该模型考虑了所有移动体以及间歇接触几何形状和比力定律。此外，已经成功实现了使用高速相机进行的实验验证。通过模型仿真，可以估算最大演奏频率，发现立式钢琴的piano带和对接弹簧的实用性，以说明三角钢琴动作中半键的快速重复功能，并虚拟调整其设置。这些结果有助于理解动作的功能和能力，并应为钢琴制造者提供有用的工具，显示出多体建模方法对消除钢琴动作行为和表演的神秘性的兴趣。