Sampling is the use of small portions or “samples” of a pre-existing recording in a new musical composition or recording.
A sample is actually a derivative work and permission must be obtained by the copyright owner. Sampling can include as little as a single note or beat and is usually not considered fair use of copyrighted material. There is no minimum amount of music that may be legally sampled.
Sampling of an original copyrighted song without permission of the copyright’s owner is considered copyright infringement.
To get permission to sample someone else’s work, you can contact one of the permission rights organizations such as ASCAP, BMI or SESAC.
The process of getting permission is called “clearing the sample.”