The most persistent myth in production is that some short duration is automatically safe. There is no such rule. Length affects how likely a rights holder is to notice or care, and it can matter to a fair-use style argument in some jurisdictions, but it is not a threshold that makes copying lawful.
You are asking two different parties
Because a track carries two copyrights, a sample generally needs two permissions: one from whoever controls the master recording — often a label — and one from whoever controls the composition, usually a publisher. They negotiate separately and can disagree. Getting one and not the other does not clear the sample.
What they will ask for
Typically an upfront fee, a share of the publishing on your song, and sometimes both. Publishing shares are the part people underestimate: a large enough share means the sampled writers own most of the song you wrote. On heavily sampled records this is how artists end up with very little of their own catalogue.
Why some records never come out
Clearance can be refused outright, with no obligation to explain. Estates in particular may decline on principle. That is why finished, well-known records sometimes sit unreleased for years, and why replaying a part with session musicians is common — you still need the composition cleared, but the master is now yours.
Practical order of operations
Identify both rights holders before you get attached to the beat. Approach early, because clearance is slow. Keep your session files so you can replace a part if the answer is no. And if you are releasing at any real scale, budget for it rather than hoping nobody notices — the cost of being wrong scales with your success.
General information only. Copyright differs by country and the details of your case matter; talk to a music lawyer before releasing anything that depends on this.
