People often ask me if I record music personally. The answer is no. I'm purely a writer. I was thinking about this question today and it got me thinking about the different skill sets rapping and ghostwriting require.
Rappers must be performers. Their instrument is their vocal cords. Intonation, breath control, pitch, annunciation and rhythm must all be finely honed. And of the intangible quality of "mic presence" must be there as well. The best rappers change their voice to match their content or the audience they want to reach. Rappers must also embody a persona. Whether they want to be or not, they embody a brand that has certain consistencies (even if those consistencies include contradiction). The best rappers are in touch with what drives them and can clearly articulate it on a record. For mainstream rappers there's also the public persona which involves media personality, fashion, and choice of music videos. Rappers who write for themselves must also be lyricists, though this is not always a necessity.
Ghostwriters are lyricists first and foremost. They must be masters of the written word. Rhythm is a necessity too because what they write ultimately has to fit a beat. A ghostwriter must also be a passable vocalist because many clients require reference tracks. There are two less mentioned skills ghostwriters must possess as well. Those are empathy and versatility. Unlike a rapper, a ghostwriter must be able to deeply understand the artistic intent of their client. They must be sensitive to that person's experiences, style and world view. They must then be able to take that information and embody it. Versatility is required if a writer wants to work for a variety of clients and customize their lyrics in a personal way.
Of course many ghostwriters rap and many rappers ghostwrite. The line between the two often blur. Artists like Rhymefest, Skillz and Kel Spencer have been able to do both because their unique mixture of rapping and ghostwriting skills. The same is true of more mainstream acts like Nas, Jay-Z, J. Cole, and T.I. Regardless the distinction is still there.