An essential step in the piano tuning process is the "test-blow" - if you've ever wondered why your piano tuner has to play the notes so viciously, here's a hint - it's not because he's hard of hearing. This vigorous strike is necessary to equalize string tension across the speaking and non-speaking lengths of the string (1), thereby avoiding the string gradually settling out of tune or slipping with the next fortissimo note. This stabilizes the string's pitch/ensures that the string will not slip with playing. As you might imagine, this wears on one's finger and wrist joints over time. In the classic piano tuning pamphlet "New Techniques for Superior Aural Tuning" the venerable master Virgil E. Smith recommends a nuanced blow where the finger pulls back *just* before bottoming out on the lowest point of key stroke, thereby avoiding impact - achieving this feels a little like the child's fantasy of giving a little hop in a plummeting elevator just before it hits the bottom of the shaft.
Actually, this advice did help and made my test blows less wearing, but it didn't fully do the trick - one inevitably knocks one's joints around here and there.
Enter the key-pounder.
There are many variations on this theme - a prosthetic finger that takes the beatings for you, with a soft yet firm tip that won't hurt the piano keys. I saw something similar to this recommended in the PTG (Piano Technician's Guild) journal several months ago, but it came together in pieces...
I cracked a hammer off an old vertical action slated for the dump which I practiced on while preparing to pass the PTG Technical Exam (2) - months later, I obtained a small wooden handle with a screw tip from a tool giveaway at a PTG Chapter meeting. One month after that, I finally got around to drilling a hole in the hammer head and inserting the handle to fashion a key pounder. I'm amazed it didn't crack, as the hammer tail is barely bigger than the screw - but it still hasn't after a week of test blows.
Voila! I've been complaining about test blows for years - I finally did something about it.
1 - The part of the string that vibrates in response to a hammer strike, thereby transferring vibration through the bridges into the soundboard, which moves air molecules that in turn vibrate our ear drums - as opposed to the "non-speaking" lengths, the portions of the string at either end – the tuning pin end and the hitch pin end – that generally do not produce sound.
2 - One of three exams required for certification as a Registered Piano Technician (RPT) – it requires the applicant to assemble and regulate a three note vertical action model, a single note grand action model, repair a broken hammer shank and install the hammer on an action model, file a hammer, create a hitch pin loop on a single string and install it, install a double string, splice a broken string, re-bush a grand hammer flange, bush the front and balance rail mortises on a piano key – all under strict time limits.