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http://fr.wikipedia.org/wiki/Partition_de_piano_mécanique

A piano roll is the music storage medium used to operate the player piano, pianola or a reproducing piano. The piano roll was the first medium which could be produced and copied industrially and made it possible to provide the customer with actual music fast and easily. A piano roll is a roll of paper with perforations (holes) punched in it. The position and length of the perforation determines the note played on the piano. The roll moves over a device known as the 'tracker bar', which first had 58 holes, was expanded to 65 and then was upgraded to 88 holes (generally, one for each piano key). When a perforation passes over the hole, the note sounds.