Royalty-free does not mean unrestricted
Royalty-free usually describes a licensing arrangement, not a universal promise that a sound has no conditions. A library may allow commercial music but restrict redistribution of the raw sample or use in certain products.
Read the license from the actual provider and save a copy or receipt. Terms can differ between free downloads, subscriptions and individual purchases.
Understand samples from existing records
Sampling a released recording may involve rights in the sound recording and the underlying composition. Whether permission is required depends on the material, jurisdiction and intended use.
Do not assume that a short sample, a changed pitch or a heavily processed sound is automatically exempt. If the use is important to a commercial release, seek permission or qualified legal advice.
Keep records for every project
Track the source of each third-party sound and the terms that applied when you obtained it. This can help answer questions from artists, distributors or platforms later.
When collaborating, tell the other people involved if a beat contains samples with specific conditions. Do not promise rights you do not control.
Choose sounds that fit your business model
If you plan to sell exclusive licenses, review whether the sample terms permit that type of licensing. Some libraries limit the number of users or require additional permissions for certain uses.
Original recordings and properly licensed sample libraries can reduce uncertainty, but the license must still be checked for the intended release.