A key bushing is the small red (usually) piece of felt that supports the key on the balance rail and front rails. It primary purpose is to allow the key to remain firm and stable while being pressed, the bushings are often lubricated to allow minimal friction so as not to interfere with playing.
On older Rhodes and Wurltizers, the key bushing are often quite old and dried out, meaning they try can allow the key to rock from side to side, and sometimes cause clucking. The bushings can be tightened by either using a key easing punch to tighten the bushing mortise, or even better rebushing the keys with a new set of felt.
If water damage has occurred on the keys, the bushings can often be very tight. Leaving them to dry out can work, and easing them with a key-easing tool and help loosen particularly tight ones.
