This post was originally published on 7/6/2015. If you have a piano with sunken keys such as shown in the photo above, your piano might have a broken elbow, or many broken elbows. This is only one possibility, but it is a common problem in spinets (upright pianos with a very short back, shorter than the top of the music rack). Spinets have what are called "drop actions" which means the action sits partially below the keys rather than on top of them as in other upright pianos. A drop action allows the overall height of the piano to be less. There are many inherent problems with these types of pianos, but elbows are the only one that will be discussed in this post.
In other uprights, the action sits on top of the keys. When a key is depressed, the back end of the key lifts and engages the action. In a spinet, or drop-action piano, the keys have a "drop wire" at the back of them that descends below the key. It has a plastic elbow at the bottom that produces the lifting action necessary to engage the action. The elbows were produced with a plastic that becomes very brittle over time and can be very easily broken. When the old elbows break, they cause the key to become non-operational and they sink as though being held down by a ghostly hand.
The fix for this problem is to replace all the elbows with a modern plastic elbow that is much more durable and will not become brittle. If you have one broken elbow, or dozens, the whole set should be replaced. Once one fails, they all start to fail. It is much more cost effective to have your technician replace them in one visit rather than multiple visits.
If you have sunken keys on your piano and you live in the Boise, Idaho area, please contact me and I will solve your problem.