However, copyright does not protect ideas, methods, systems--only the way that one expresses those things. Nor does copyright protect anything that is mechanical, anything that does not involve choice, or criteria concerning whether or not one should do a thing. For example, the results of a process called declicking, in which one mechanically removes impure sounds from old recordings, are not copyrightable. On the other hand, the choice to record a song digitally and to increase the sound of violins or to bring up the tympani constitutes the results of conversion that are copyrightable. Moreover, if a work is protected by copyright in the United States, one generally needs the permission of the copyright owner to convert it. Normally, who will own the new--that is, converted- -material is a matter of contract. In the absence of a contract, the person who creates the new material is the author and owner. But people do not generally think about the copyright implications until after the fact. PETERS stressed the need when dealing with copyrighted works to think about copyright in advance. One's bargaining power is much greater up front than it is down the road. PETERS next discussed works not protected by copyright, for example, any work done by a federal employee as part of his or her official duties is in the public domain in the United States. The issue is not wholly free of doubt concerning whether or not the work is in the public domain outside the United States. Other materials in the public domain include: any works published more than seventy-five years ago, and any work published in the United States more than twenty-eight years ago, whose copyright was not renewed. In talking about the new technology and putting material in a digital form to send all over the world, PETERS cautioned, one must keep in mind that while the rights may not be an issue in the United States, they may be in different parts of the world, where most countries previously employed a copyright term of the life of the author plus fifty years.