Sound production on an upright piano is a process that uses the piano keyboard, vertical strings, and hammers on top of the strings to generate a desired musical tone. The damper pedal is often used to vary the duration of the sound. First, a piano key is pressed on. This action signals the hammer that corresponds to the key to strike the appropriate vertical string, allowing the string to vibrate. Vibration of the string creates a musical sound. If the piano key is pressed with greater pressure, the hammer would strike the string harder and faster in order to make a louder sound. If the damper pedal is used, the hammer first strikes the string, then lifts off to allow for the string vibrations to continue and for the sound to trail.