Studios that produce pop music typically have in-house songwriters. They might work collaboratively, they might reuse ideas from each others’ work, they might even dig up unused lyrics written by someone else and add their own elements. When people say that pop music is produced in an assembly line, that’s not an indictment, it’s an observation.
In the demo and production stages, some songs get passed around to different singers, producers and writers, similar to how scripts get passed around to different screenwriters in the movie business. A song may go through many iterations, and by the time it’s deemed good enough to release, it’s a sort of Frankenstein’s monster of ideas contributed by a bunch of people.
Also, writers of a sampled song may be listed as co-writers if a significant portion of the melody or lyrics are copied.
Idk how true this is, but I read that some in-house songwriters will make superficial changes to everything they can in order to have a credit, which gets them royalties. I imagine if you do this enough times, you end up with a monster hit to your ‘credit’. No idea what kind of royalties songwriters get, let alone when it’s split a dozen ways, but even 1c/play is gonna add up if you get your name attached to the biggest song of the year.
Writing pop music is nothing like the vision you have in your head. In your head, a person or band has this brilliant idea for a new song, they get out pen and paper and a guitar or piano, they write it all down, practice it, and go to record it.
Instead, pop music is a capitalist venture. A publisher or producer decides they want to create a new product. They hire professional songwriters and producers to come up with it in a sterile environment, they find a face for it (a pop “musician”), they record it, they spend hundreds of hours in their DAW software making it sound absolutely perfect, then they release it under the illusion that “oh this is Rihanna’s latest masterpiece she came up with”. It’s just like a hollywood movie, overly polished, overly produced, totally fake.
Same reason it can take many writers to write a TV show, a movie, commercials, comedy sketches. It is often several people writing the music, then several writing the melody and lyrics. Most pop songs are done by a large number of people throughout the process, much like a TV show or movie production.
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