Of the over 10,000 parts that make up the marvel of the piano, most are wood, felt, leather and metal. Wood can warp or break, felt and leather compress and wear, metal can fatigue. All this happens with use and age, and occurs eventually on all pianos. Thankfully, most of these parts can be repaired or replaced. Keeping everything on your piano in sound working condition will not only make it more enjoyable to play but will help maintain its value.