A Music Roll is used to operate a Mechanical organ or Orchestrion and contains the music to be played. Originally made of paper, modern rolls are sometimes made of thin plastic or mylar.
The music is stored by means of perforations. The mechanism of the instrument reads these, as the roll unwinds, using a pneumatic sensing device called a tracker bar, and the mechanism subsequently plays the instrument.
A piano roll is a specific type of music roll, and is designed to operate a player piano.
Image:DrehorgelRollen.jpg|Selecting a paper roll of music. Image:DrehorgelLochkarte.jpg|Music roll in place showing a pattern of holes representing notes. Image:DrehorgelVentile.jpg|Tracker bar, which reads the punched music roll. Image:DrehorgelnPfeifen.jpg|Each hole is connected to a valve in the interior of the organ which operates the organ pipes such as these wooden ones.
