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Line Scanning to Save Player Piano Rolls

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Brent D. Johnson

Although to modern ears the music of a player piano is a sound track for the gilded age, the instrument that made ragtime a ubiquitous part of the American musical experience relied on one of the most sophisticated recording technologies of its day.

As a line-scan camera system images backlit punch holes in a player piano roll, software determines the area, perimeter, centroid, length and width of each hole and identifies them in green.

The player piano was one of the first practical machines in wide distribution to encode recorded instructions from a binary format. Before solid-state memory and magnetic tape, basic computing devices used punch cards to store information. The pianos are not electrical, however, but purely mechanical. As paper filled with punch holes unravels on a roller, the holes admit small pegs, or spindles, that trigger a corresponding pitch on the piano.

This player piano roll from the collection of Meta Brown is a recording of "A Perfect Day" from the early 1900s.

To fabricate these rolls, an artist such as "Jelly Roll" Morton was hired to perform a piece on a recording piano. The instrument punched holes in the paper as the musician played. Frequently, words and graphics were printed on the rolls to allow people to sing along.

Rob Schoenberger would like to preserve the piano rolls by making digital copies of them. He is president of Agris-Schoen Vision Systems Inc., a small company that makes machine vision systems for a variety of applications, including US currency inspection, finger-print analysis and speedometer calibration. He became interested in the player piano rolls through a friend and former classmate, Meta Brown, now Webmaster of the Automated Musical Instrument Collectors Association.

Collections decaying

Schoenberger said that many player piano rolls are decaying, and that soon there may be no record of them. The Smithsonian Institution and the Library of Congress have extensive collections. The rolls are typically 12 inches wide and may be up to 100 feet long. Taking pictures of them with a standard camera would be silly, he said. Line scanning is much more suited to the application.

He is developing a scanning device to simultaneously record the punch holes and the printing on the rolls. It will have two spools, an optical encoder, two Dalsa Spark 14-inch 1k30 cameras, a stepper motor and a Horizon 4 LC frame grabber from i2S-Line Scan of Niskayuna, N.Y., that uses Parallelex software. A halogen backlight coupled with fiber optic bundles will shine through the punch holes, permitting one camera to line scan the data. Another light will illuminate the front of the roll so the second camera can image the graphics. Conceivably, the data could be hooked up to a musical instrument digital interface (MIDI) and played directly from the roll.

Although Schoenberger doesn't expect there to be a significant commercial demand for the product, he does feel that his company's contribution to preserving these artifacts of musical history makes the effort worthwhile.

Photonics Spectra
Aug 2002
Accent on ApplicationsApplications

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