首先定义两个方向:1、向前-受敲击力而运动的方向。2、向后-向前的反方向。 在制作立式钢琴的后期——整理阶段,常常会发生击弦“抖”（一次按下琴键,弦槌多次击弦）或“噎”（快速连续弹奏同一琴键,弦槌不能连续击弦）的情况。既便在钢琴的使用中,有时也会遇到此问题,给弹奏带来很多困惑 First define two directions: 1, forward - subject to tapping force and the direction of movement. 2, backward - forward in the opposite direction. In the production of upright piano in the late - finishing stage, often will have struck the string “shake” (a press the keys, the hammer multiple strums) or “噎” (fast continuous play the same key, the hammer can not continuous strike String) situation. Even in the use of the piano, sometimes encounter this problem, to play a lot of confusion