Freakin' LOVE this forum. Some really knowledgeable dudes here.
That being said, AVOID the Harry Fox Agency at ALL COSTS. They're a dinosaur and charge WAY too much for licensing. I was under the impression they handled licensing/permission for recording cover tunes but I guess they could also be in the sample-clearing field as well. Just FYI, if anyone here is every looking to release an album of cover tunes or an album with a cover (or covers) on it, check out LimeLight. They do EXACTLY what Harry Fox does but for MUCH more reasonable rates. I believe their site is
www.songclearance.com.
Now in terms of copyrighting original songs, there have been some very recent legal developments that have placed the interests of large corporations & huge, established artists over those of the songwriter. The most famous recent case is the one between Rebecca F. & The Memes & Lady Gaga; Rebecca (full disclosure: she's a mutual friend here in Chicago) claims Gaga stole parts of her 1999 tune "Juda" to create the track "Judas."
This is an extremely fucked-up case, and the judge who presided over it made a horrible decision in my humble opinion. Rebecca can not only prove beyond ANY doubt that Gaga had complete access not only to the tune itself but to the ProTools sessions from the recording of "Juda," and while Gaga's song definitely contains elements that are not in "Juda," her song also definitely contains elements that were CLEARLY lifted from Rebecca's song.
Rebecca has a federal copyright; all the evidence in the world that Gaga had access to the song and can prove she heard it prior to writing "Judas" (which isn't even necessary under US copyright law; a writer can infringe upon another writer's content unknowingly, meaning they created a similar work without nefarious intent, which results in a 1x damage payment, whereas if the plaintiff can prove beyond a doubt that the defendant had access to the original song and therefore acted nefariously, the damages are 3x; the most famous case of this is Huey Lewis vs. Ray Parker Jr., where Lewis proved that Parker Jr. not only created a song ["Ghostbusters"] that was extremely similar to his own ["I Want a New Drug"] but that Parker Jr. intentionally ripped it off); and she can also draw direct personal connections between herself and Gaga which accurately & effectively illustrate the path down which the information traveled to arrive in Gaga's hands, but all of that wasn't enough to win the case. They're appealing.
Point is, yes, users have posted accurate information regarding "real" copyrights (the ones you register with the Library of Congress for a small fee) and "inherent" copyrights (the ones that exist the instant you write something original and release it to the world), but when it comes down to it, all that matters is how powerful you are. This is just another step towards the world we have allowed the powers-that-be to create, one in which corporations are all-powerful and have rights traditionally reserved for individuals (Hobby Lobby, anyone?), even though they bear NONE of the responsibilities that individuals must carry in order to receive their individual rights. It's nonsense. And it has to stop soon or we're all screwed. I mean, screwed even more than we already are.
Lastly, the web is chock-full of info regarding clearing song samples for use in derivative works; I also just checked and found out that yes, it seems LimeLight does in fact handle sample clearing. They have a fantastic informational page on the subject:
https://songclearance.com/How+to+Avoid+Sampling+Disasters:+A+Step-by-Step+Guide+to+Clearing+Samples
Hope that helps. Feel free to message me with any questions; I'm always willing to help fellow musicians/songwriters/artists.