Copyright—a set of exclusive rights to use certain content and to prevent unauthorized use by others.

Derivative work—incorporating pre-existing copyrighted work into a new work that is itself copyrightable. Creating derivative works is one of the exclusive rights reserved to the copyright owner, unless it falls under the fair use exception.

Fair use—the exception to the exclusive right where the content is “transformed” and used in a new way. Fair use has been summed up as the right–in some circumstances–to use copyrighted material without asking permission or paying for it.

To evaluate fair use of copyrighted material, the courts consider four factors set out in 17 U.S.C. 107:

1. the purpose and character of the use
2. the nature of the copyrighted work
3. the amount and substantiality of copying, and
4. the market effect.

For most courts, the most significant factor in this analysis is the fourth factor–effect on the market. If the new work reduces demand for the original work, then it’s very difficult for the secondary author to claim fair use. On the other hand, if the use does not compete with the original (a parody, criticism, or news report) it is more likely to be fair use. Courts also have applied the doctrine of fair use to visual collages and musical works, such as 2 Live Crew’s “Oh Pretty Woman.”

So what about a mashup? Such as the wildly popular “The United State of Pop” by DJ Earworm or the hard-to-come-by “Smells Like Booty” (the amazing mashup of “Smells Like Teen Spirit” and “Bootylicious”). This art form has been growing in popularity since 2003 and is seen in everything from the works of DJs, to Academy Award® montages, to small theater and choral productions.

Are mashups derivative works? Absolutely. Is this fair use? Probably so. Its certainly transformative and unlikely to replace demand for the original. We won’t know for sure until Avril LaVigne sues DJ Earworm.