Decent article as a window into the world of piano adjustments. Tuning is but one task among many for a piano technician. At a decent conservatory, there will be at least one staff technician in charge of keeping whatever fleet of pianos the school has in tune. Concert pianos are always tuned before performances and practice pianos less often. They're also in charge of keeping a piano in tone.

I think most people don't realize how sensitive a pianists ears and hands can be, especially if one has achieved some measure of fame and is accustomed to good instruments. Not only the tuning must be exact but the action of the keys must be perfect: how much force/weight the key needs to be depressed, how fast does it bounce back up, what kind of a force curve it has going down (first heavy then light, medium all the way through), etc. Then, when the hammer actually strikes a string, what does it sound like? A piano technician (as opposed to a tuner) might poke at the hammer with a needle to soften the sound, or pour on some lacquer a la Steinway to make the sound brighter. Each key has to have the same kind of resonance, spacing, action, and sound as all the others.

Even I have run into these kinds of minute problems. Back at Brown, I played my senior recital on a Bechstein. This particular instrument was very bright (absolutely gorgeous for Beethoven) but I wasn't playing Beethoven. I was playing almost all romantic repertoire. Certain notes in the bass could really ring out, which was good, but I had to hit the other notes harder to compensate. There was a middle section (a bit above middle c to 5-6 notes above that) that was more "dead" than the rest of the piano so I had to press with more weight there. High notes got shrill if I didn't watch how harsh my hands were. Legato passages had to be overheld more so that they don't sound like brilliant leggiero passages from Beethoven. All this and more players just figure out as you get used to the instrument.

The same thing holds for all instruments, or even professions. There's so much more than what one sees under the surface. Little tricks, stories, quirks...and all so fasincating.