The hammer is one of the most important parts of the piano. It is what swings and hits the string, making the string emit sound! The hammers are made of a molded wood core which is often either mahogany or hornbeam and than the tip is covered with a soft (typicaly high quality) wool felt head, (as you can see in the image above). The hammer is specialy engineered in a process of stretching and gluing the felt in layers to the wooden core. It is important that the felt head is firm enough for a bright tone yet resilient and soft enough for proper string contact.