If your piano is producing clicking noises when you play it, it may be time to contact a professional piano repair technician. However, it may be possible to diagnose and repair the problem yourself if the problem is not too severe. The level of difficulty involved in making the repair depends on the type of piano and the nature of the problem. In most cases, clicking noises have something to do with the piano's action. The action is the part the piano that contains the strings and the series of hammers, dampers and other elements that strike the string and allow it to resonate.
Remove the piano cover to access the action mechanism. On upright pianos, the cover that encloses the action is in two parts, an upper and a lower cover. Flip the top cover backward. The upper section of the cover may be secured to the piano with screws or may simply set in place on the piano. Remove the upper section from the piano if it is not screwed on. The bottom section may be secured with screws as well or it, too, may simply sit on the piano. Unscrew the bottom section with the appropriate screwdriver and remove the bottom section from the piano.
Play the piano and identify the piano keys that are producing the clicking sounds. Clicking noises are usually isolated to individual keys. Play each piano key, moving from the left side of the piano toward the right. Take note of each key that is making a clicking noise.
Play the piano key or keys that are making a clicking sound and diagnose the problem. The most likely culprit is the interaction between the damper and the hammer for the individual key. When a key is pressed, the damper is lifted off the string and the hammer strikes the string, causing the string to resonate. A few issues may be the source of the problem, but the most likely culprit is the hammer and damper. One of these components may be loose, causing them to come into contact. Loose joints can be corrected with a little dab of white glue. The hammer head may be the problem. If it is loose or rattles, it may be striking the damper. Secure the hammer head to the shank with white glue. If the joints and hammer head are secure but the damper is still coming into contact with the hammer, trim a small portion of the edge of the damper arm with a thin pair of cutting shears.
If the source of the clicking is not obvious, the action mechanism needs to be removed, repaired and then replaced. This requires professional tools and expertise.