As your piano tuner Wilmington DE, Kenneth Keith Piano Services, I often encounter pianos where a hammer strikes twice when the key is struck only once. The explanation is useful for all piano owners, because this situation is often mistaken by the piano owner as indicating that the piano needs tuning.

Piano technicians call this situation “bobbling hammers.”  When a key is struck, the notes will sound two or more times in rapid succession. It is a sign that the piano action is severely out of proper adjustment, which in the industry is termed “regulation.” The term would be used like this: “The action is out of regulation.”

Some background information is necessary for a proper explanation. A piano action has ten major adjustments in order for it to work properly. The reason it is so complicated, is that it is relatively difficult, mechanically, to get a piano hammer to strike a string once, and then rebound and be caught, so that it does not strike the string repeatedly. The piano action is called an “escapement” action, because the wooden elements that push the hammer toward the string escape, or change position when the hammer is 1/8″ way from the piano string. The hammer then continues toward the string based on its own momentum, not because it is being pushed. Because the element, called the “jack” has escaped, the hammer can rebound away from the string and be caught by a “back check” and thereby hit the string only once for each strike of the piano key.

If the action is out of regulation, then the proper escapement of the jack often does not occur. As a result, the action does not complete properly, the jack does not escape, and the hammer hits the jack on the rebound from the string. If this occurs, the hammer will be pushed toward the string a second time, resulting in the “bobbling hammer.”  Of the ten adjustments for proper regulation of a piano action, if any one of four of those adjustments are out of regulation, the result can be a bobbling hammer. The job of the piano technician is to analyze the operation of the action and to determine which of those adjustments need to be corrected in order to restore proper function to the action. The most common causes are hammer blow and lost motion regulation. Less common are key height or dip shallowness, which reduce proper key travel.

If you have questions about the proper functioning of your piano or need any type of piano tuning Wilmingon DE services, please consult us at Kenneth Keith Piano Services, your Wilmington piano tuner. We also provide expert piano services in Philadelphia, as well as the Eastern Shore Maryland and Southern New Jersey areas. We are always happy to help.