Not sure I agree with your premise; nothing really fell down, it just went somewhere else as the culture changed. The preteen girls in my last kids' group at work think r&b (and rap) are doing just fine. I don't like what they like, but that's 'cause I'm over 35.
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Rough answer, though:
- '60s Soul, like Aretha, Al Green, earlier Motown = church-based virtuoso singing + virtuoso studio musician band + tape and tube/ribbon equipment; (and a smattering of other influences, e.g., some jazz chords, some Afro Caribbean rhythmic influence, etc.).
- This morphed in the '70s into funk. Sly Stone was a transitional figure into this style. The vocal performance became slightly less important as the arrangements got more harmonically and rhythmically sophisticated (more jazz and Latin influence, new instruments and effects, more complex chord progressions and horn charts). The recorded sound got cleaner and maybe thinner, as overdubbing increased and solid state recorders and consoles came in.
Examples: Curtis Mayfield, Parliament, Earth Wind & Fire, Isley Brothers, and so on. Also note the huge influence of
James Brown's rhythm sections in making grooves more sophisticated.
- By the mid '80s, it was starting to be possible to replace live backing bands with sequenced synthesizer, sampler, and drum machine parts, still recorded to tape. The turning point I remember is Janet Jackson's hits, like "Nasty" and "Let's Wait a While," which Jam and Lewis produced with the Ensonic Mirage sampler and some other stuff. The glossy DX7 sound got big too, because it was the first decent polyphonic synthesizer that was affordable. (Rap was coming in, but the early stuff, e.g. Sugar Hill, was cut just like a soul or funk record -- rapper plus great band, to tape). Early sequencers had a low resolution, so the music felt a little stiffer sometimes, compared to the soul and funk stuff before.
This stuff I just mentioned might be the beginning of the aesthetic shift you asked about.
- Eventually, computer recording and better samplers (MPC, etc.) became common. Certain arranging tricks, like stacking up enormous numbers of background vocals, grew out of the move from tape to computer and the greater number of tracks available. The elimination of live rhythm sections was complete, and that changed the feel somewhat. The church-based acrobatics in the vocals became more pronounced, especially for female singers, since the backing tracks sometimes were relatively simple (similar to soul).
Also, by now the jazz generation of musicians had passed on, so a certain amount of harmonic sophistication started to disappear by the '90s; there were still great producers, but some of them weren't as well-schooled as, say, Johnny Pate (who produced Curtis Mayfield) or Bernie Worrell (who did a lot of composing for Parliament), people who really knew chords and orchestration.
This is where I got off the R&B bus, so I don't have specifics for you re artists, etc..
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Have you read
Nelson George's book?
Not that I have, but it seems relevant.
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Hope this helps . . .
