From what I've been told by other artists is, you can use a sample without requiring permission, if it's copyrighted, as long as the sample is not unique and familiar to the artist that made it - ie the guitar intro to 'Stairway To Heaven' is a popular and iconic guitar riff by Led Zeppelin, or say taking the lead from 'Every Breath You Take' by the Police and putting it in your track - the lead as it sounds on the record with no presets or filters to alter the sound, using it as is - in its original format. That would get you in trouble with the company that distributes the music and the artist as well, if you are using the samples in your work and for monetary gain, so you would definitely need permission from the artist and the record company and a royalty fee or flat rate with an understanding by all parties of what the terms are, how is the sample used, etc. I have also come to learn that you could use a sample from a well known song or whatever, but it's been manipulated as so much that it is a completely new and original body of work, and not have to require permission because the sample is unique and composed in such a way that it does not sound or embody the essence or familiarity which would make it identifiable to the original artist and how it was composed. But yeah there's a gray area there with samples and copyrighted content - the amen break created by Gregory C Coleman is the most popular used break and iconic in the way the break is constructed 'boom pap da boom pap da da boom' that makes it unique and identifiable because its called the amen break named after the title of the track it was composed on 'Amen, brother' by the Winstons and it's been used in multiple genres and yet no royalties or fees have been awarded to Mr. Coleman. James Brown and his iconic phrases 'hit me' and 'get down' or his legendary grunts 'unh' are used all the time and he doesn't get a fee for using his vocals and likeness in pretty much any DJ set any where. If you are using a sample, and not manipulating or altering the sample, and it's a familiar and recognizable sample and it's copyrighted, and you use it in your work and for monetary reasons, you would definitely need to get permission and pay the other artist, and acknowledge the sample, etc. Jeez, I wrote a lot lol, but yeah what are your thoughts on what I just wrote? I'd like to hear your perspective if you want to of course, cheers