Napster has launched a new version of its music-swapping service that marks its first step toward blocking music based on the contents of a file and lays the groundwork for a new subscription service. Released on Sunday, Napster's beta version 10 of the software for its music download service introduces new technology to build a database of music based on acoustic fingerprints, the data that represent the unique sound recording of a file. That database is the first step toward blocking music based on fingerprints. A filter must have a database to check in order to decide whether a specific work should be blocked. Such technology also would enable Napster to better identify music for a future subscription service scheduled to launch July 1, according to a company spokesman. Napster has been building a filter to block copyrighted music in order to comply with a court injunction issued in March. The injunction stems from a suit filed in December 1999 against Napster by the recording industry, which charged the startup with copyright infringement. Napster has been stepping up its filtering efforts since US District Court Judge Marilyn Hall Patel named a technical expert last month to advise her on whether Napster is using all available technology to satisfy the injunction. Before the launch of beta 10, Napster had been blocking music primarily based on text searches of artists, songs and file names, leading the recording industry to complain that users were bypassing filters by misspelling names. Napster licensed the fingerprinting technology from Relatable. Every once in a while the new version of Napster will generate a fingerprint of a file that a user is sharing and send it to the Napster service, which will store the data with other identifying information about the file, Napster explains to users on its site. In addition to helping to block music, that database can be used to identify music that is being legally downloaded by Napster users when the company launches a subscription service this summer. Such information is critical to determining the royalties on such downloads. Copyright 2001 The Industry Standard