Do we need to sing a hip hop melody adhering to a scale/pitch?

Question

Do most hip hop and rap artists sing in correct tune with and in the same key as the instrumental part? Should the vocals be in a scale(Major/minor/blues etc)?

Answer 1

Do most hip hop and rap artists sing in correct tune with and in the same key as the instrumental part?

I think the best answer here is Yes, many do, but maybe not most.

The vocals for hip-hop and rap are often very different from pop vocals, but many times there is singing in the same key as the instrumental backing. Actual rapping is normally not in any key, and some rap and hip hop has no singing in it. For some rap and hip-hop, the versus are not sung on any specific pitch but the chorus is.

Two things that make hip hop and rap vocals unique are:

1. The prevalence of obvious "auto-tune" or pitch correction on sung parts. This is so popular it's hard to pick just one example, but for me I think of Akon's Don't Matter as an example. This also is an example of rapping without definite pitch (sort of, see below) for the verses and pitched and auto-tuned singing for the choruses. And it's an example of point two.
2. Even with rapped sections or songs where there isn't a firmly fixed pitch, the rapping is usually semi-pitched. That means that the speaking/rapping is done in a specific vocal range with certain up and down movements in tone, and if someone performed the same rap it would sound weird/different/wrong if they didn't reproduce the range and speaking tone.

Note that a lot of hip hop and rap backing tracks do not establish a firm pitch sense or key. There are often unpitched percussion tracks and short samples that are pitch shifted, weakly pitched, or not cohesively defining a key. Here I'm thinking about old-school 80's style rap like Public Enemy.

Should the vocals be in a scale(Major/minor/blues etc)?

I think this is the same question. If the backing tracks establish a key, then that key will have one or a few scales that go along with it. If the vocalist(s) want(s) to sing along with the backing tracks, they will have to follow any scales that are part of the key established by the backing, or else it will clash.

Probably the best way to understand hip-hop and rap vocals is to sing/rap along with the vocals on your favorite tracks, and then sing/rap the same parts on your own. Notice where you voice clashes and doesn't sound the same as the artist, and pay attention to what you have to do exactly the same way to make it sound right versus what you can do your own way that still works with the song. You should feel the singing versus rapping and all the nuances that go into that kind of performance.

Many people snobbishly dismiss (or maybe I should say "dis" - hah) rap vocals as "not really music" or something like that, but they are often very challenging. And sounding convincing as a rapper is usually not at all easy to do. For instance, no matter how much I practice, with my voice if I tried to get on stage and rap some Chuck D lines from Public Enemy, I'd be laughed (or maybe chased) out of the venue. But I could probably fake Eminem if I had to and I could definitely pull off a bit of the stuff from Hamilton if I practiced a lot. The best way to understand rap and hip hop vocals and how you can sing them effectively is to get in and start doing it and find your voice and style.

Answer 2

Sometimes in hip hop there's a polykey thing going on where the voice is in a different key from the backing track or the backing track layers are in different keys.

I think this comes from the early days of sampling when people couldn't easily adjust the keys of the samples they were chopping from vinyl, but regardless of the historical origin, it can make some songs really sophisticated harmonically. It's definitely opened a lot of people's ears to poly keys.