The notes produced on a piano are the result of at least one string being struck with a small hammer. The strings vibrate at different frequencies to produce different notes. The string frequencies are determined by the wire used and its length, width, tension and density. The strings in pianos are made with extremely tough wire that is hard enough to chip the blades of a regular wire cutter.
The strings in a piano have a variety of characteristics in order to produce a diverse range of pitches. A high note is made on a light, short string under more tension, where the opposite is true of a low note. When the keys of a piano are depressed, the hammer hits the string to create the note. It quickly flies away from the string so as not to stop the vibration, which is what creates the sound. The hammers in a piano are covered with tightly wound felt, and the felt can be adjusted with special needles if the piano begins producing a harsh sound. Different sizes of hammers are used for treble and bass notes. The soundboard of a piano is what amplifies the sound that is emitted from the instrument.