When I moved home from college years ago, all of my flute sheet music went missing. I have slowly been trying to locate the pieces I had. I saw that several of the duets I needed were on the "Ultimate Sheet Music" CD for sale on eBay. The advertisment says this is legal because the music is "Public Domain." What qualifies this as being such? Is it a certain number of years old? Certain amount of time without renewal of the copyright?

The CD came in the mail. It was $9.99 and has tons of the music I am missing. Of course I have to print it all and that costs money, but nowhere near what it would have cost to purchase it again.

I guess what I'm asking is: Is this legal?

Public Domain regarding music I believe is 50 years after the death of the composer is considered public domain.

Funny, I thought about printing out my own copies of things and found it cheaper to buy the music rather than print it out myself. I guess I picked the wrong instrument.

Yes, I'd always heard that it was cheaper just to buy the music. However, when I calculated it, it's much cheaper. Take the Kuhlau Op. 10 Duets... there are 34 pages total. At 10 cents a copy that is $3.40. I get copies here for only 5 cents so I pay half of that. If you go to fluteworld.com the same piece is $16.50 + shipping.

I guess it might be a little more difficult if you are not networked to a photocopier since these do come as PDF files, but even Kinko's here does it.

That's why I asked if anyone is sure that this is legal because it just seems too good to be true.

I believe it is 75 years, but maybe someone can look this up to make sure...

Patrick is more correct than I am.

United States Copyright Law
US copyright law is found in Title 17 of the United States Code and is administered by the US Copyright Office. " Terms for Copyright Protection", a U.S. Government publication, summarizes the current duration of copyright protection for published works as follows:

Works created after 1/1/1978 - life of the longest surviving author plus 70 years - earliest possible PD date is 1/1/2048
Works registered before 1/1/1978 - 95 years from the date copyright was secured.
Works registered before 1/1/1923 - Copyright protection for 75 years has expired and these works are in the public domain.
The Sonny Bono Copyright Term Extension Act was signed into law on October 27, 1998. Prior to the Sonny Bono 20 year copyright term extension, copyright protection for works registered before 1/1/1978 was 75 years; therefore, compositions registered in 1922 or earlier entered the public domain on 1/1/1998. The 1998 copyright extension did not extend copyright protection from 75 to 95 years for songs already in the public domain so . . .

The Good News - works published in the United States in 1922 or earlier are in the public domain even if they are not yet 95 years old.
The Bad News - no new works will enter the public domain until January 1, 2019.
You can confirm the above information about public domain and copyright protection in "Extension of Copyright Terms", Circular 15t, of the U.S. Copyright Office. Specifically the last paragraph of Page 3 states in part "Works published before January 1, 1923, have fallen into the public domain." We suggest that you print this circular and keep it as part of your public domain research materials.

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) U.S. 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.

Rule of Thumb for Public Domain Music
Works published in the United States with a copyright date of 1922 or earlier are in the public domain in the United States.
Copyright protection outside the USA is determined by the laws of the country where you wish to use a work. Copyright protection may be 95 years from publication date, 50 to 70 years after the death of the last surviving author, or other criteria depending on where the work was first published and how the work is to be used.