a striking mechanism for a string instrument , such as a piano or a grand piano , which has , for each string , a hammer , which , via a power transmission , is brought to strike the string when the associated key in the keyboard of the instrument is depressed . the mechanism includes first and second checks having , respectively , first and second check zones for , in mutual engagement , stopping and temporarily retaining the hammer during rebound . a magnetic or magnetizable material is placed in each check zone to generate a magnetic field which causes the hammer during rebound to obtain a much safer and softer braking than is the case in conventional striking mechanism . thus , the risk of the hammer rebounding and striking the string in an unintended repetition strike is eliminated .