Even today, there are copyrighted protections for every piece of classical music that is written and/or performed. This is covered under the “musical works” protections and stipulations. This means that anyone who holds a copyright for music will have the exclusive right to reproduce it, to make copies of it, to perform it and much more. The terms of copyrights will last during the life of the author plus 60 years past their death.
The person who holds the original copyright in the US is the person who created the original expression in a piece of musical work. This work could have more than one author and the copyright can be transferred. But, if the work was say, made for hire or made with some sort of commission, the person who was commissioned will be the one who will hold the copyright. In music, a copyright can be issued for two reasons, the musical work and any recording of it. The copyright holder then has the single exclusive right to make records of that piece of music. Then once it is recorded a second copyright will come into existence for the music.
After a piece of original work has been copyrighted, anyone who wants to use this music in some sort of production will have to get permission from the person that has the copyright. This permission will generally cost some money and then the person paying for the permission will receive some sort of license to allow them to legally use the material. So, if someone wants to perform, reproduce, translate, record, adapt any piece of copyrighted classical music they are required by law to get permission first, otherwise they can be sued.
Most US copyright laws that are given are similar if not exactly identical to International copyrights. Most countries will follow the norms on all copyright protection that has been established through different multilateral conferences. The most important conference that was ever held about this issue was the Berne Convention for the Protection of Literary and Artistic Works. This was sponsored by the World Intellectual Property Organization which is actually a division of the United Nations. There are also some protections that can be covered by the World Trade Organization's Trade Related Aspects of Intellectual Property. This means that most countries all have agreed to similar terms about music being protected in the same manner.
Understand that if you are interested in using any classical music that is protected that you really need to be careful before you use it. Make sure that you know how the music is protected and then find out how you can get permission to use the music for your needs. Otherwise, you could end up getting into some pretty hot water.