USA Copyright Law for Musical Works
United States copyright law is found in Title 17 of the United States Code and is administered by the US Copyright Office. Legally a copyright means that a musician, author, or artist has a "limited duration monopoly" on anything he creates. The US Constitution, Article 1, Section 8, grants the government power "to promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries". A work is automatically under copyright protection from the moment of creation, but to legally file for copyright infringement the copyright must be registered with the copyright office. Registering a composition provides public notification of copyright and allows the copyright owner to demand damages and attorney's fees if his copyright is infringed. If you use a song under copyright protection without the owner's permission, you are opening yourself to possible legal action.
United States Copyright Duration for Musical Works
The current duration of copyright protection for published Musical Works in the USA as follows:
Until 1998, the maximum copyright protection for works published before 1978 was 75 years; therefore, compositions registered in 1922 or earlier entered the public domain on 1/1/1998. The Sonny Bono Copyright Term Extension Act was signed into law on October 27, 1998, and increased maximum copyright protection to 95 years for works published 1923 thru 1978. But the 1998 copyright extension did not extend copyright protection from 75 to 95 years for songs already in the public domain so . . .
Detailed copyright term information can be found in Duration of Copyright, a U.S. Government publication. Remember that copyright laws define when a work IS UNDER copyright protection, not when a work is NOT UNDER copyright protection. So determining public domain status can be difficult to comprehend because the public domain exists in the absence of any possible copyright protection. Additional information about The Sonny Bono Copyright Extension Act is found in Extension of Copyright Terms, Circular 15t of the U.S. Copyright Office. Other U.S. Government Circulars about copyright law are also available on the US Copyright Office website.
International Copyright Law
The Berne Convention is an international treaty standardizing copyright protection since 1886. In 1994 a General Agreement on Tariffs and Trade (GATT) was signed by 117 countries, and the World Trade Organization (WTO) was created in Geneva, Switzerland, to enforce compliance with the agreement. GATT includes a section covering copyrights called the Trade-Related Aspects of Intellectual Property (TRIPS). US law was amended to be essentially consistent with GATT by the Uruguay Round Agreements Act (URAA) in 1994 and the Sonny Bono Copyright Extension Act in 1998. Despite GATT, copyright protection varies greatly from country to country, and extreme caution must be exercised on all international usage of any intellectual property.