What key should your beat be in?

The honest answer to which key should this be in is that it barely matters, and that almost everybody asking has a different problem. What matters is staying in one. A beat in the wrong key sounds fine; a beat with one note outside the scale sounds broken, and that is the difference this question is usually reaching for.

Why almost everything is minor

Open any hip hop, trap, drill or lo-fi record and you will almost certainly find natural minor. It is not a rule and it is not mysterious: minor gives you a darker third and a flat sixth and seventh, which is the sound the entire lineage of this music is built on. If you want the default that will never sound wrong, it is natural minor.

Everything below assumes minor. If you want the same information for major, it is the same information with a brighter third.

Picking the root

If nobody is singing or rapping over it, the root is arbitrary. Pick one and move on — the emotional character people attribute to particular keys is real for orchestras with open strings and effectively imaginary for a synth. What actually changes is where the notes sit on your keyboard.

If somebody is going over it, the root is not arbitrary at all: it should sit where their voice is comfortable. That is a conversation with them, not a decision you make first and hand over.

The one practical consideration for an instrumental is register. A root very low leaves your bass in the mud; very high and you run out of room above the melody. Somewhere around A or C is unromantic and works.

The rule that actually matters

Stay in the scale. Seven notes, repeating in every octave, and every one of them will sit against every other one. Almost every beat that sounds amateur in a way people cannot name has one note in it from outside the scale, usually in a melody written by ear on a chromatic grid.

This is worth enforcing mechanically rather than by concentration, especially under a time limit. The studio here has a scale lock that snaps a note to the nearest one in the key as you place it — it is on by default, and the whole reason it exists is that this mistake is invisible while you are making it and obvious the moment somebody else hears it.

A progression that works, if you need one

• i — VI — III — VII. In A minor: Am, F, C, G. It is everywhere for a reason.
• i — VII — VI. In A minor: Am, G, F. Darker and shorter, so it loops better over eight bars.
• Just i. One chord for eight bars is a completely legitimate answer, and a great deal of trap is exactly this.

Over eight bars the third option is more often right than people expect. There is not enough time for a progression to be the interesting thing, so the interesting thing has to be the drums, the bassline or the sound.

When to break it

Deliberately, once you can hear it. A borrowed chord or a chromatic passing note is one of the most effective things available and it is completely unavailable to somebody who cannot yet tell the difference between that and a mistake. Learn the fence before you decide where to put the gate in it.