Music Score Watermarking

Abstract

Music publishers, authors and/or distributors have high quantity of music scores in their archives. In classical music, the original music piece is normally kept in paper format, since its production goes back to many years ago. At present, only new light and popular music pieces are in symbolic notation formats. Light and popular music have a limited lifetime when compared with classical music pieces. The duration of the copyrights for that kind of music is about 60-80 years. Content owners are very cautious to transform their classical music pieces in digital format for e-commerce purposes, because they consider it as a highly risky process which could ultimately lose their copyright ownership. The situation is different when it comes to light and popular music, being market life shorter. According to content owners’ opinion, e-commerce for music distribution cannot be accepted, unless adequate protection mechanisms are provided, as highlighted in WEDELMUSIC (www. wedelmusic.org) and MUSICNETWORK (www.interactivemusicnetwork. org). They accept to have their music protected only if it is possible to control while at the same time the users exploit content functionalities according to the established permissions and prices. To cope with these problems, mechanisms for protecting digital musical objects are used (see Table 1). In this article, only problems and solutions for protecting and watermarking music scores are discussed. Most music scores are still kept in paper format at publisher’s archives. A first step to transform them into digital documents can be transforming them into images with a scanner. Another possible solution can be found in transforming them manually into symbolic music with a music editor. Obviously, this latter solution is very expensive, since the music has to be totally retyped. The use of very efficient Optical Music Recognition (OMR) software, similar to the Optical Character Recognition (OCR), seems to be quite unlikely in the next future. Currently, their recognition rate is close only to 90%, which makes this approach not too much reasonable when compared with retyping (www. interactivemusicnetwork.org, see assessment on the Working Group of Music Imaging). Music images or symbolic music are obtained after music sheet digitalization. In the event of images, no further music manipulation is possible at the level of symbols. On the other hand, images can be easily viewed in any operating systems and with plenty of applications. The symbolic music gives several advantages in the score maintenance and manipulation; it allows the user to perform changes on the music, such as to justify it, change the page settings, add ornaments, accents, expressions, view single parts or the whole score, and so forth. The drawback consists in all these possible operations being performed only if the music editor is available: professional music sheets are produced by expensive and professional music editors. It is well known that music sheets are distributed in paper format among musicians. Therefore, it seems that such digitizing process is useless. Practically speaking, Internet music sheet distribution, meaning from publishers to consumers, can only be achieved using digital formats. Distribution among users, as it occurs now with photocopies, could be made even via digital music sheets, as Napster did with audio files. Please note that on P2P (peer to peer) application there is also a quite significant distribution of music scores (www.interactive musicnetwork.org, read report on Music Distribution Models of the Working Group on Music distribution).

Key Terms in this Chapter

Staff: Line: Each single line of the music score staff. The pentagram is made of five staff lines.

Fingerprinting: Used for calling the hidden serial numbers or anything else that should allow to the copyright owner to identify which reseller broke the license agreement. It is used for the multilevel document distribution.

Watermarking: Process of inserting a hidden code or message into a digital or analog object. As opposed to steganography, it has the additional notion of robustness against attacks. As the name suggests, the additional data (the watermark) is added in order to protect the digital document from copyright infringements. Even if the existence of the hidden information is known, it has to be hard for an attacker to destroy the embedded watermark without destroying the data itself.

Fragile Watermarking: Techniques that do not guarantee the watermark presence after few document manipulations.

Steganography: Techniques that allow secret communication, usually by embedding or hiding the secret information (called embedded data) in other, unsuspected data. Steganographic methods are based on the assumption that the existence of the covert communication is unknown and they are mainly used in secret point-to-point communication between trusting parties. As a result, steganographic methods are usually not robust, that is the hidden information cannot be recovered after data manipulation.