If you are using music or recordings that are protected by a copyright, you are legally required to pay royalties for using the song.  Most Web sites will only be using songs as background music and can apply for a general license from the writers and publishers of the songs you would like to use. 

ASCAP and BMI are two of the largest organizations that provide general copyright licenses, but if you only want to use one or two specific songs, you should contact the artist or the record company that own the copyright to the song composer, writer, publisher, performer, musician(s), producer, distributor, or record company 

If you’re using a song that was written over 100 years ago, it probably falls under public domain.  Nearly all of the music written by classical composers like Mozart and Bach fall under public domain. However, unless you are using a copy you played yourself, the performer or musician(s) that played the song own the rights to their performance of the song.

Avoiding Copyright Infringement
Current technology makes it fairly easy to combine material created by others - film and television clips, music, graphics, photographs, and text - into a multimedia product.  Just because you have the technology to copy these works, that does not mean you have the legal right to do so. If you use copyrighted material owned by others without getting permission, you can incur liability for hundreds of thousands or even millions of dollars in damages.

Most of the third-party material you will want to use in your multimedia product is protected by copyright.  Using copyrighted material without getting permission - either by obtaining an "assignment" or a "license" - can have disastrous consequences.  An assignment is generally understood to transfer all of the intellectual property rights in a particular work (although an assignment can be more limited).  A license provides the right to use a work and is generally quite limited.

If you use copyrighted material in your multimedia project without getting permission, the owner of the copyright can prevent the distribution of your product and obtain damages from you for infringement, even if you did not intentionally include his or her material.

You will not need to obtain a license to use copyrighted material if:
1. It meets “fair use” requirements (like many non-commercial applications such as education, research, or news).
2. It falls under public domain (works that are not protected by copyright).
3. It involves factual statistics or other data.

Don't make the mistake of believing these myths about copying material from the Net:

Internet Myth #1: If I find something on the Net, it's okay to copy it and use it without getting permission.

While you are free to copy public domain material that you find on the Net, generally you should not use copyrighted material without getting permission from the copyright owner -- whether you find the material on the Net or in a more traditional medium (book, music CD, software disk, etc.).
 
Internet Myth #2: Anyone who puts material on a Web server wants people to use that material, so I can do anything I want with material that I get from a Web server.

Individuals and organizations put material on a Web server to make it accessible by others. They do not give up their copyright rights by putting material on a Web server. Also, the person who posted the material may not own it.

Internet Myth #3: It's okay to copy material from a Home Page or Web site without getting permission.
 
Much of the material that appears in Web sites and Home Pages is protected by copyright. If you want to use something from someone else's Home Page or Web site, get permission unless permission to copy is granted in the text of the Home Page or Web site.

Posting Material
And don't believe these myths about how copyright law applies to putting copyrighted material owned by others on the Net:

Internet Myth #4: It's okay to use copyrighted material in my Web site as long as no one has to pay to visit my Web site.

Unless your use of the copyrighted work is fair use (see Fair Use, later in this article), you need a license to copy and use the work in your Web site -- even if you won't be charging people to view your Web site. (You also need a public display license.)

Internet Myth #5: It's okay to make other people's copyrighted material available on my Web server so long as I don't charge people anything to get the material.

Copying and distributing copyrighted material without permission can be copyright infringement even if you don't charge for the copied material. Making material available for others to copy can be contributory infringement.