Don't worry, you'll soon get the hang of it - I'm still learning.
Copyright law is confusing enough when considered one nation at a time, and even more so when more than one country's laws come into the equation.
The composer (and how long he/she has been deceased for) is only one factor. You also have to consider:
- Who is the editor? Is he/she still under copyright? (different laws for urtext, but urtext may still have a named editor.) Google his/her name and see what you come up with.
- What country is the piece published in? (Is is in the public domain in the country of origin?)
- What year was the piece first published? (I have just aquired a copy of a Schubert (1797-1828) song which was lost, re-surfaced as a manuscript in the estate of a deceased antiques dealer in 1991, and was first published in Germany in 1999, edited by a person who is contemporary and very much alive. Even though Schubert (as the composer) is long since PD, this particular piece will not be for quite some time to come.
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)
There are many other things to consider. If you try to find out as much information as you can about one piece at a time, you will be amazed how quickly you will learn and soon you will be able to look at a piece and say "that's still under copyright" or "that's PD here, but not in country X".
I still think, however, that it would be nice if IMSLP was hosted in Afghanistan. (No copyright laws at all there.)
Aldona
“all great composers wrote music that could be described as ‘heavenly’; but others have to take you there. In Schubert’s music you hear the very first notes, and you know that you’re there already.” - Steven Isserlis