The hook in hip-hop song writing
When hip-hop began, many critics thought that it was not music at all. After that phase had passed, critical scorn of hip-hop focused on groups that used explicit lyrics. Now, for better or for worse, hip-hop and rap music have become a part of the mainstream of American music and culture; something that is not widely welcome in the underground of hip-hop. However, from the earliest days of simplistic party raps, to the gangsta error, and throughout both the mainstream and underground world of hip-hop, there is one way that hip-hop has never gone against the grain of pop music: songwriting structure. While the lyrical content of rap songs can be quite different, the songs themselves are structured in a familiar way, usually verse chorus verse.
However, hip-hop being what it is, the chorus is almost always referred to as the hook. Parts of the song that are not actually in the structural place of the hook can sometimes be referred to as "the hook", for example, on the crossover hit "Hey Ya", the long outro is the actual "hook". But in most circumstances, "the hook" is merely a hip-hop term for the chorus. One of the reasons that it is not referred to as the chorus could be that a hook is not always sung, (or even spoken) but can be anything, including a scratch, a sample, or a different beat.
The importance of the hook in hip-hop music comes from several causes, some intrinsic to the music itself, some having to do with hip-hop's acceptance into more pop oriented radio formats.
One of the main reasons that hip-hop songs generally need a hook is the nature of an MC, especially a lyrical MC. Despite all the hype, flash, and excitement that rappers create around their personality, a lyrical solo from a rapper is not always in itself exciting. It is exciting in its own way, but no more so than, for example, a saxophone solo. Some of the best MCs, for example Nas and The GZA, have rather understated delivery, and a song with nothing but uninterruped rapping would lose its energy at a certain point. A chorus, with exciting lyrics that are easy to understand, and catch the listener's attention, is needed to carry the song. Related to this is the fact that, despite some revisionists attempt to paint hip-hop from the beginning as a deliberate, intellectual activity, the idea of MCs rhyming in cyphers for the purposes of pure lyricism is not the basis of hip-hop. The basis of hip-hop is parties and club shows, which involve crowd interaction and call and response chants. Hip-hop is meant to be participatory, and the simplest way to be participatory is to have some simple, repeated lyrics for crowds to sing along with.
Another reason that hip-hop songs need hooks is that as much impact as hip-hop has had on popular music, popular music has had a large impact on it. R&B music, meaning a more smooth, melodic style of black music, with usually less confrontational lyrics, was one of the most popular music formats when hip-hop was first developing, and in order for hip-hop songs to get radio play, they needed to include a more melodic hook. Also, besides for seeking commercial appeal, soft melodic hooks are a natural counterpart for the rhythmic sounds of hip-hop. The Wu-Tang Clan, a band who is undebatably hardcore, has used soft hooks to great artistic effect on songs like Can it be that it was all so simple? and All That I Got is You.
Some types of hip-hop songs don't use hooks: many times a story telling song will not, or a posse cut, which is just uninterruped rhyming by a group of rappers. However, for most rap songs, for reasons both artistic and commercial, a hook is neccesary.