Fair use basically doesn't apply to recordings of songs. The practitioners and those in the business of different categories of creative works can establish different standards for qualifies as fair use. In the early Nineties, the music industry basically decided that there was more money to be made from licensing samples than from fostering the creation of works that use samples.

To be more precise, a fair use defense on a sample not being a substantial or essential part of the original work (if the source can be recognized, the sample is substantial) or it not causing financial harm (because paid sample licensing exists) is dead. Defense based on your work being commentary or parody of the original work is still available. Theoretically, a defense based on transforming the sample is still available but in practice if the source can be recognized, the use wasn't sufficiently transformative.