the way that hiphop has aggressively sampled vocals and instrumentals from the '60s to the '80s is kind of fascinating, like is that a one off? does the collapse of "regular music" mean they have to keep diving further for ever deeper cuts, or does the genre ossify into the use of a dozen standardised amen breaks and wilhelm screams deployed in ever more complex fractal patterns, like what's the arc of progress here
it's like the recorded music industry flourished from the '50s to the '90s and that brief burst of creativity spawned a classical lexicon that generations of future artists would constantly return to, like Confucians vainly trying to restore the Zhou dynasty by proper performance of the rites
There's a number of things going on at play here that span the technological, the economic, and the legal, and remember that the active keyword in "music business" is "business".
To understand hip hop's development in a compositional sense, you have to understand the landscape that is happening in NYC in the 1970s with the emergence of block parties, and the fact it's working off a lot of just contemporary records, playing off just a bunch of turntables, and turntables plus a sound system would always be cheaper than a full band. It starts downstream of dub and DJ toasting. When you are establishing what the sound of old school hip hop is entirely driven through what is essentially handmade samples with turntables and a mixer. This is what is leading the sound from the 1970s through the early 1980s.
Once you get to the 1980s, the landscape changes; drum machines are starting to show up, and so are synthesizers, and they're getting cheap, and the sound they have is not fantastic, so what you do is you can now combine samples with that. You think of say, Eric B and Rakim's Paid in Full, you have both a drum machine and sample going! Rock and pop are doing a similar thing (check out the Cocteau Twins for a similar use of drum beats vis a vis Marley Marl!); you can point to so many records built around just using a ton of samples because now you have the capability to do that. This period is a point of really strong musical development, but that's going to run into an issue the minute you hit 1991 because you get a landmark case that is maybe the worst case ever: Grand Upright Music, Ltd v. Warner Bros. Records Inc.
There's a lot to complain about it, not least the fact that the judge uses "Thou shalt not steal" as the reasoning behind it (!) but the end result is: if you want to sample anything, you have to get it cleared with copyright owners of that sample, and because of Cherry Hill Music v. Universal Music Publishing (regarding New Order's "Run 2" accidentally sounding like John Denver's "Leaving on a Jet Plane" during the guitar break!), if you sample anything, they get credit as well!
So there's specifications for what it means to be a sample and to be transformative, which in and of itself is an issue. The shorter the sample, or the more obscure the sample, the more likely you are to get away with it. Or you release it in a mixtape format without expectations of monetary value BUT without the need for credit. Or you almost recreate it with studio musicians, at which point it's something else.
All of those become possible options, because this is 1991. The Akai MPC, one of the earliest fully programmable and playable samplers that you could own in your own home (as opposed to the Fairlight CMI, which is specifically a thing for studios), comes out 1988. And 1991 is also when Pro Tools drops, followed by dozens of Digital Audio Workstations, DAWs, drop.
The scenario has completely changed. You now have an incentive to not to take a direct sample and work off of it, but to start with a single sample, maybe a single drum hit, maybe one bass pluck, and then build on top of that. Maybe you have one really good sample you're gonna be using and you're gonna highlight it, but the rest? That all gets reduced to just the sound of one hit. Something like Lord Tariq and Peter Gunz's direct sample of Steely Dan's "Black Cow" on "DĆ©jĆ Vu" is just not possible. Instead you look at the Wu-Tang Clan's "Protect Ya Neck", and the drums are based off one loop (though the snare is from something else), and the bass and piano are default samples on the keyboard sampler RZA is using to produce. Or you combine a ton of samples and they're obscure and the problem becomes pulling them out and making sense of them. This is the strategy that goes to the underground. If you're Dr. Dre, though, you get a bunch of studio musicians to recreate samples in-studio.
Because nobody wants to clear samples anymore, the sound slowly starts to change, especially towards Southern Hip Hop and SF Hyphy. The economics are also changing bit by bit. If clearing the samples isn't really a thing you do anymore, then you change the sound to be centered around the drum machine and the synthesizer, and you try to get some kind of robotic funk going. The end result is that at this point, there's a separation between "sampling" as looping a played groove, and "sampling" as the origin of a sound on top of which you're going to build things.
As a separate thing, this is all driving alongside R&B and neosoul, which have also hitched itself to hip hop, because it is genuinely musically exciting at this point in time for so many people, especially the producers.
The economics very quickly change the genre as well. You can only afford to work off a ton of samples if you have the willingness and time to dig through sample after sample. Or you buy a sample pack and work off your DAW because in the year 2000, a computer, a MIDI controller and Pro Tools made a hit within reach. Hell, you don't even need a MIDI controller. And that means the genre becomes a rocket when MySpace and especially when Soundcloud roll around.
If Joe Schmoe #1 can make a beat in his bedroom in like 2011 and sell it to Joe Schmoe #2 for $200 and Joe Schmoe #2 raps over it in his mixtape and it becomes a hit, then there is an underground economy picking up at which point the sample has been completely divorced, because samples have separated from the reality. As you go through trap, jerk, rage, drill, the gamut of underground hip hop, there's no need for samples anymore, and if you do it's a sample pack that you're using because getting a specific synthesized sound is annoying.
So to choose to go back to a sample-heavy style is either because you are deliberately calling back to older styles (see: Kendrick Lamar's To Pimp a Butterfly which deliberately uses samples as part of the tradition of Southern California hip hop and funk and is calling back to it), or because you're trying to do an underground, Madlib/MF DOOM/Dilla/etc thing, which is a completely different vibe and the point is that it uses this collage of obscure samples.
Now, there are a number of stylistic choices sometimes; Death Grips's Exmilitary mixtape samples a number of classic rock and punk songs and even synthpop because it's semi-preoccupied with it and toying with those ideas. Later on, because it's more experimental, it's also working off that. Same thing with somebody like Lil B and his aggressive use of sampling, because he's operating off internet distribution more so than traditional distribution. Those are still underground hits! Those are not The Big Leagues! The people who can clear the samples at the high level are Kanye West sampling Nina Simone for instance, you need to have high visibility and to be in a major label to then say "and now I wanna sample this specific artist" and that has to become the flag you plant around it and call attention to the sample. It is hard as hell.
In short, samples start to become less of a key part of hip hop as you enter the 1990's due to legal and technological factors, and by the 2010's, the economics of it have taken over and there's no point to a sample anymore unless you are deliberately working in a style that wants to use samples.
