I've had my Yamaha Disklavier for over 25 years and the only attention it’s needed is the occasional tuning. However, I noticed some time ago that the most used keys around the middle creak when you press them. It's fairly quiet but you can hear it if you press the keys slow enough not strike the stings and you can feel the resistance as well. The top and bottom keys are fine. The noise seems to be coming from the key itself rather than the hammer action inside the piano.

I'm fairly handy at fixing things and wondered whether any experts out there had come across this before and had any ideas about whether it's a simple enough job and if so, what to do and what not to do. It may be that it happens on any piano but there may be extra precautions on the Disklavier having the key actuators.

Any advice is appreciated. Thanks!