But are production teams any different than what Phil Spectre did with Carol King and Goffen and the Wrecking Crew, or Berry Gordy, THe Funk Brothers and the Motown staff writers and the other big producers in NYC and Nashville?
That's a really interesting observation, and I'd have to say that there are similarities, but also significant differences mainly related to the most important thing in the business -- ownership of the intellectual property..
You could probably add Muscle Shoals to that list, too.
I'm most familiar with Motown, partly because I'm a Detroit guy who grew up during the Motown era, and partly because one of my closest friends was appointed to analyze and evaluate the facts in the litigation here between Motown and the writing team of Holland, Dozier, Holland, which was since settled (and his report is an unsealed court record so he was able to talk about it). So I have a lot of information about Motown in particular.
Motown's team was a label-owned creation, and the studios (though in what was originally a home) were not what we'd call a "project studio" today, and it was hardly "shoestring." The place was rebuilt as a studio. Motown even had their own mastering room, record cutting lathe, etc., and the gear was certainly first class in its day. All of the performers, writers, etc., did work exclusively for the label, and HDH produced and wrote exclusively for Motown artists.
Phil Spector also formed a record label, and his staff wrote and produced for Philles artists. Again, songs were recorded in commercial studios that were booked for the various sessions. Carol King and other Brill Building writers were songwriters pitching to artists, but they were free to sell to whomever and they didn't get involved in production (though in Carol King's case, obviously, she became an artist).
So both of these cases were a little different from production teams that are unaffiliated with labels and particular artists, and that write, produce, and in some cases supply the backing tracks that are used in the master recording.
So while there are similarities, these are major differences, especially when it comes to how the intellectual property is handled.
I'm not familiar enough with the history of the Wrecking Crew to be able to draw a comparison. I know they existed, and that's about it.
Muscle Shoals was definitely a team, but the songwriting didn't come from them for the most part. For example, Aretha Franklin wrote her own material, Wilson Pickett came in with his own material, etc. What they had was a particular band, a particular producer, and a "sound" for other artists to record with. But they weren't songwriters for the most part. And of course, they were simply a "go to" studio, producer and band for one label or another during the time they were making hits. They did remain technically independent.