Open Piano Surgery

I broke my piano recently during a fairly intense practice session for an upcoming concert. Three of the keys, C# (2 below middle C), middle C, and F stopped responding. The hammers wouldn’t go.
Luckily I know a good piano technician.
He pulled out the “action” of the piano, discovered that the reaction springs were loose and proceeded to adjust them. What amazes me is the amount of engineering that goes into a modern piano. Looking at the hammer mechanism, I’m fairly amazed at how it can hold up to my heavier piano pieces–pieces that involve laying a good percentage of my body weight into the keys.
Music and engineering. Good stuff.