I actually did not notice the black key noise when playing through on board speakers. It's when I played with headphones on, that my granddaughter mentioned a little clicking sound. That, along with some other SX -900 users at PSR Tutorial pointing out the noise, made me aware of the problem.

Since I really never noticed the noise, I would have done nothing, but when I found out, it kinda bothered me, and since Yamaha was willing to pay for an evaluation and repair if needed, I decided to have it done.

Maybe sometimes you are better off not knowing. But if you're like me, once you're aware of it, ya gotta do something about it.