Because of copyright laws, legally using popular music in a marketing video is possible only if it’s in the public domain or if the artists have made their music available for free (via the Creative Commons license, for example).

Websites such as Open Source Music provide libraries of tracks that you can use for free. You can find many usable tracks on these sites, typically produced by up-and-coming musicians who want to find their audiences. Some, such as Kevin Macleod at Incompetech, can even produce custom music for you at relatively affordable rates.

Classical music from the public domain can often be a good match. For example, Stanley Kubrick originally intended the stock music he chose for the movie 2001: A Space Odyssey as a placeholder until a score was written, but he kept it.

Be careful: Classical music can be used only if you record it yourself or use a recording that’s older than 70 years. Otherwise, the musicians who played the classical song have the right to royalties.

Before you use open source tracks, you must understand the exact licensing conditions under which the song is published. The Creative Commons license has several different levels, some of which prohibit commercial use. Even if a song isn’t published under the traditional copyright, it’s still illegal to use it outside of its license conditions.