There are many rules of thumb that circulate as to how much of a work you can copy without committing copyright infringement. None of them have any basis in the law. Each case is different and has to be evaluated on its own merits.
Copyright law is very strict. If you copy a copyright protected work without the permission of the author, you have committed copyright infringement and you may be sued. Although there is a defense of fair use, it does not cover very many uses. If your sample is recognizable as coming from the original song, it is likely that you have committed copyright infringement.
On the other hand, common practice is much less strict than the letter of the law. For example, people often post videos that they have created on YouTube and include commercial music in the video without the copyright holder’s permission. Technically that is copyright infringement and the author could sue. But no one has ever been sued for this practice. You can probably get away with using the sample on YouTube. I call this the “Will anybody really care?” analysis.
Be aware that common practice and copyright law are often at odds with each other. The fact that you followed common practice is no defense to a copyright infringement lawsuit. It is not a defense to a copyright lawsuit to say that everyone else is doing it too. You will probably not get in legal trouble for using a sample on YouTube, but you might.
You can often use common sense to determine when you can copy a work. As a rough rule of thumb, you should consider if the person whose work you are copying would likely be offended by your use of their work. If the answer is yes or maybe, do not copy. If the answer is no, then proceed at your own risk or consult a copyright attorney. Since there are no easy rules, do not expect a copyright attorney to be able to give you a definitive answer. Usually all they can say that it is or is not likely to be considered copyright infringement.
This answer is not intended to be a substitute for personalized legal advice. I have presented only an overview of the legal issues. There are many nuances and some exceptions to general legal principles. Real problems are very fact based.. If you have a specific legal problem, you should consult an attorney. You can find more useful information on my law firm website resources page at www.marshallcomputer.com or you can contact me directly at firstname.lastname@example.org or (206) 524-0655.
I cannot agree more with Mr. Marshall. There is the "30 second" myth going around, which says that copying clips of 30 seconds or less is considered fair use. This is indeed a myth and has no legal support in the Copyright Act nor in caselaw.
It is a common misconception that there is some definite percentage of a work that you can copy without reaching full-scale infringement. That is not true. Even a few seconds of a larger work can be infringement and conversely copying an entire work could not be infringement.
Your question cannot be answered without evaluating the specifics of what you want to do. That said, when it comes to sampling music, there is very little you can get away with. Very little.
Remember, fair use is a defense to copyright infringement. It is not. Permission slip. Just because your action could be construed and defended under the fair use doctrine, you're going to be defending a lawsuit to raise it. Get permission. Depending on what you are sampling, you could purchase a limited license for the work for such a purpose. This is not a place to be cutting corners.
Contiguglia / Fazzone, P.C. / Standing up for you, when others sit down! / www.contifazz.com / Just because I answered your question, that does not create an attorney - client relationship between us unless and until there is a written fee agreement in place formalizing our attorney - client relationship.
I am attaching an essay on fair use. Make your own call (safe or out) after reading it
Licensed in Maryland with offices in Maryland and Oregon. Information here is general, does not create a lawyer-client relationship, and is not a substitute for consulting with an experienced attorney on the specifics of your situation.
The "legal" amount of "sampling" [infringement] is zero if you want to be safe. As a practical matter, you can get away with whatever you get away with, and that depends on the tolerance level of the copyright owner. If is it is enough to hurt their sales, it is enough for them to take notice and to sue you. Remember, however, the copyright makes it there playing field and you are like a fan running out onto the field. Maybe the referees get you and may be the cops depending on how blatant you are. Stay behind the sidelines and you will likely be safe. Get in their way and you can expect to get removed from the playing field and punished. Read 17 USC 106 and 501.
I am not your lawyer and you are not my client. Free advice here is without recourse and any reliance thereupon is at your sole risk. This is done without compensation as a free public service. I am licensed in IL, MO, TX and I am a Reg. Pat. Atty. so advice in any other jurisdiction is strictly general advice and should be confirmed with an attorney licensed in that jurisdiction.