It doesn't matter whether Dilla or Shadow cleared this that or the other, it doesn't matter if it's one second or 1 minute and is doesn't matter if it's flipped beyond recognition - generally speaking if you sample someone else's work without their permission then you are probably infringing their copyright - it's certainly best to take the assumption that you are.
Whether you get caught is a completely separate matter. The more people listening to it and the more recognisable the sample, the higher the chances someone is going to spot it.
I know someone said get a lawyer to write you a contract pushing the onus on your client to clear samples, but I am fairly sure that you cannot use a contract to effectively say 'I might be committing commercial copyright infringement, but that's your problem' - I don't believe any legal system allows you to use a contract to absolve yourself from an illegal act, be it civil or criminal. Regardless, your client would have to be a complete dumbass to sign a contract like that
But yes in reality, 99.9% of beats never get popular enough to be noticed by anyone connected to the copyright holder.
Decision is yours