Blow distance, key dip, letoff, aftertouch: these are key elements to regulating a piano action. How these relate depends on geometry of parts and their assembly. In general, a longer blow distance needs a deeper dip for a given letoff and aftertouch. And a shallow dip needs a shorter blow. If blow distance remains the same, deepening the dip will increase aftertouch. If key dip stays the same, shortening the blow distance will increase aftertouch. Increasing letoff distance also increases aftertouch, but interrupts blow earlier, thus reducing control and power (unless letoff was causing interference by being too close).
If you made it through that paragraph, excellent. There’s more to say. Here is a story from the “trenches”.
About five years into my becoming a piano technician, my teacher flipped me a job, a fund-raiser at a well-known museum featuring a 19th century German upright from its collection. I arrived four hours before showtime.
The case and action, including original ivory keytops, were admirably crafted and pristine in appearance – a joy to meet – but this instrument completely did not play. Hammers bobbled or barely reached the strings. Some dampers didn’t lift at all. The piano was over a whole step flat and all the screws were loose. A custodian helped me roll the piano offstage and down a hallway into a well-lit storage room where I could see better and would not be disturbed. He then went to find the Special Events person.
The biggest challenge, apart from time, was going to be dip, or rather, lack of dip. Severe moth damage, wear, and compression had distorted geometry throughout the piano.
I experimented with a sample key and found the paper, card, and cloth front punchings extremely fragile - I should touch these as little as possible. Blocking the hammer rest rail up with a mute, I took up the lost motion and roughed in letoff. It still barely played.
Meanwhile, the head of Special Events showed up and I outlined the problem. She gave me permission to do what I could. The show had to go on.
I took the action out and stood it to one side for screw tightening. A couple of the whippens were already dropped below their broken bridle straps.
What were the options? Removing frontrail card and paper punchings risked disintegrating what was left of the soft punchings. Removing the backrail cloth would provide more dip, but both key-landing noise and large change in elevations vetoed that idea. So, I loosened all screws holding down the balancerail and added strips of business card to raise the rail.
When tightening the action screws, other bridles broke, so I had to insert the keys one-at-a-time. I did remove a calculated amount of paper and card punchings as I went - just pulling on them with tweezers, they split and came out.
As I went, my other need was to improve damper lift, which was way too late. Since the dampers were also very fragile, I shimmed out the lift rail and regulated the dampers by gross-adjusting the spoons.
This was both fast and slow work. Objectives: least done to make each note play without damaging parts or eroding materials. Means: roughed-in-only adjustments using the tools at-hand.
From there, I shimmed the rest rail with cuttings of temperament strip, touched up lost motion, touched up letoff, thumb-adjusted backchecks, pitch-raised twice, and tuned. Yikes! “Crude but effective”, a modus operandi commonly-practiced by technicians I knew at the time.
I did have a dip block with me, but I lacked sufficient new punchings and the extracted punchings were a mess. And I simply did not have enough time. So, even or not even, rough dip and approximate aftertouch were achieved.
I just made the deadline. After that, the museum called me instead of my teacher. He was, as it turned out, about to make a career change that would take him out of state. But whether or not this was an intentional hand-off, it certainly was a trial-by-fire launching, full of self-teachable moments and resulting in a great gig that helped establish me. Later, I had the opportunity to undo my extra shimming and partially restore the action.
Takeaways? One role of key dip can be mediator, balancing whatever else is happening in the action, allowing hammers to play, piano to be tuned, and musician to make music. The crude rough-regulating I did got the job done (with assistance from supportive miracles like no strings breaking or jacks coming unglued). Here were the most basic pragmatics of key dip.
I also learned the importance of external calm to piano work. In a way, the more impossible the situation, the more important our body-language that all will be well, particularly in a concert setting. My teacher had told me this, and he had taught me about key dip as an important regulation step. But only under the pressures of an unreasonable situation did the reasons come into focus, the hierarchy of choices manifest. There was no time for insisting on specs or making excuses, say for dampers not working. Things were the way they were and much depended on doing the least possible as fast as possible to solve the problem. I’ve come to think such simplicity is often characteristic of best solutions.
In the next part, I shall discuss methods of fine-tuning dip and look at dip’s role as articulator.