Every Year

This happens to me every year.  As winter approaches, I trade in my light short-sleeved shirts for heavier long-sleeved ones, but with the sleeves rolled up.  Then I finally stop rolling up the sleeves.  Next thing I know, I'm tuning a piano and as I hit a note with my left hand, I hear an intermittent but unmistakable click.  What was that?  I try again; no click.  Wait, there it is again, what is that?  Loose hammerhead?  Loose whippen heel?

Duh, it's the button on my shirt cuff hitting against the keytop.  I fall for it every year.