I see this problem regularly with upright pianos, especially ones that haven’t been maintained. But this problem can also occur on instruments that have undergone a temperature and humidity shift. It’s also commonly found on old pianos with compressed or worn parts. It’s called lost motion. The name is appropriate because it refers to the simple fact that the piano keys are not “connected” to the hammer assembly. There’s a gap in between. So while you’re pressing down the keys, quite often, the hammers of the piano are not moving because of this gap. Essentially, the motion is lost. The lights are on, but no one’s home. You’re putting in the effort at the key but nothing is happening for the first few millimeters. Why is this a big deal?

Dip
On average, pianos have about 10 millimeters of dip – how far the keys travel downwards. If the hammer isn’t moving for 2 or 3 out of 10 of those millimeters, then that represents 20 or 30 percent of the key travel where the hammers are not moving. Having a piano touch that is out of alignment doesn’t do you any favors as a performer. The result of lost motion has 3 substantial side effects:

The first is that the piano feels sloppy. It feels inherently that there’s too much travel in the keys and that the piano feels somehow loose. Your intuition is correct if this is happening. If the hammer is missing the motion at the outset of the key, the hammer will only be rotating in the bottom of the keystroke and will trick your brain into thinking that the keys feel loose and sloppy. It almost feels somehow disconnected and hard to control. This is incredibly frustrating when trying to play quietly.

The second thing that will happen is that the piano keys will feel light. The lost motion gap from the key to the hammer butt will make the piano feel inordinately light. This is due to the fact that the hammer rotation is delayed. Rather than feeling like the key and the hammer are moving in tandem, this lost motion means that only the keys are moving until the gap is closed.

The third and often more overlooked aspect is that the piano may misfire. Because the backchecks are lowered with the gap, hammers may bobble and create unwanted strikes of the hammer.

The solution? It’s quite simple really. It involves rotating the capston, which is the adjustable screw attached to the key. As the capston goes higher, the gap is closed and makes the hammer move at the appropriate time. Ask your technician and they will easily fix the problem.

Is there a point of too much? Absolutely. You can’t keep turning the capston and “create” a heavier action. When the parts align, that’s it. You can’t go any farther. If you do, a scenario called pre-loading occurs in which the hammer is moved forward and is resting on the capston. This too can have adverse effects where the repetition lever may not return properly.

Lost motion is difficult to get your head around in terms of what it is. But once you know about it, you’ll sense it immediately. And having a technician complete this task is so satisfying. It’s like resetting the piano to factory specs and the change is instantaneous. The piano will feel positive, more controllable and give you more control of touch and dynamics.

Kayserburg

Ritmuller

Pearl River

Steinway Ad

More Piano Articles