Key Height and Dip

Remember the teeter-totter on the playground when you were young? One end went up when the other went down, and balancing the weight of the kids on either end was always part of the fun.

Well, the keys on your piano share traits with teeter-totter. Maybe that’s why we play on them….

When you press on a piano key, the end under your finger goes down, while the other end goes up. The end that goes up connects with the action in some way, and it ultimately transfers the energy from your finger to the hammer (and thus to the string). That’s a lot of functionality for such a simple object.

Like a teeter-totter, a piano key has a spot near its middle where it teeters. To keep the key balanced on that spot, a steel pin passes through it. That pin is driven into the “keybed” (the frame under the keys) and serves to stabilize the key so all it can do is teeter up and down.

There is another pin that sticks part-way up into the key at the end you press when you play. This pin is also driven into the keybed, and its purpose is to the keep the key from moving sideways.

If all the pins did was to keep the keys stable, that would be useful. But those pins also anchor key “punchings”, felt and paper rings that sit under the keys. Felt punchings come in several thicknesses and help make key movement silent. Paper punching are much thinner and are added to the felt ones for fine adjustments. The punching on each pin have different purposes.

The punchings around the balance pin (the one in the middle of the key) determine the key’s height. The punchings around the front pin (the one that keeps the key straight) limit how far down the key goes when you press it. That distance is called “key dip”.

Why do punchings matter? A piano key’s height is the foundation on which a properly regulated action rests. If the key height is wrong, nothing else will work correctly. And key dip is the first movement of many that transfer energy from you to the string. If the key dip is incorrect, all the other action movements will be thrown off, as well.

The basic geometry of the teeter-totter and its support and control anchors are the basis of a well-regulated and enjoyable piano.

You can check key height yourself by looking at the front, vertical face of the keys on your piano. What you see of the key front should be a square, not a rectangle. The tops of the keys should form a smooth line, with no surprises sticking up (or down). Key dip is a little trickier to gauge since it varies among different makes and models of pianos.

Why not just do yourself and your piano a favor, and ask your piano technician about the key height and key dip on your piano. It only takes a minute to measure them, and you might be very glad you took the time.