With the exception of more recent Contemporary R&B (as opposed to 50s and 60s R&B/Soul) and mainstream pop, Hip Hop seems to thrive on features in comparison with other genres, even other traditionally African American genres (which, by way of community, was my initial hypothesis on why it visibly features other artists, as opposed to just casually employing them in the more general liner note credits)
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One significant thing is that often times these “featured” artists can easily not actually be involved in the production and no one knows any better. This is way easier in some forms of music than others.
For many rap and to a lesser degree some modern R&B, often songs are constructed in parts and they can just take an unrelated “featured” artists who has say a 30 second snippet of anything they made and just fit it into a track the original artist is making, without any collaboration needed (this doesn’t mean collabs don’t happen, just that its not required).
Usually the producer may go out to try to get featured people to sell or give them snippets of their content to use as marketing for the song/artist doing the full track. These generally take extremely minimal effort for a bigger name artist, who may already have recorded and stored dozens, if not hundreds of small unused clips of songs they just have sitting around that never made it anywhere. Maybe it was even the same producer
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