A type of keyboard assembly used in electronic keyboards and synthesizers. During manufacturing weights are added to the plastic keys, usually by glueing pieces of metal to the underside of the part of the key where a players fingers make contact. The extra mass, combined with stronger springs causes the key to be harder to set in motion down, and depending on the spring and how much weight is added will change the speed and force with which it returns to rest. The result is a keyboard action that feels or “plays” much more like mechanical piano keys, which is sometimes preferred among players. A further development in keyboards is the use of hammer action key assemblies, where the key actually moves a mechanical hammer, making it feel even more like a real piano key.