“In many cases these publishers are basically getting the revenue off of composers who are dead for a very long time,” Mr. Guo said. “The Internet has become the dominant form of communication. Copyright law needs to change with it. We want people to have access to this material to foster creativity. Personally I don’t feel pity for these publishers.” Those who “cling to their old business model,” he added, will simply fade away. But publishers point out that users of the site can miss the benefit of some modern editions that may be entitled to copyright protection — and thus not part of the public domain — because of significant changes to the music, such as corrections and editing marks based on years of scholarship about the composer’s intention.