I ran across an overlooked technique that would definatly help a rapper on any beat. This secret weapon is called "timbre" which is defined as the combination of qualities of a sound that distinguishes it from other sounds of the same pitch and volume. This is also what distinguishes the difference of any two instrument you listen to like the difference from a piano versus a guitar. Continue reading below:
The way a rapper can utilize this on rap beats is simply making their voice noticably different as the beat goes on. For example on the Fetty Wap track entitled, "Jimmy Choo" the popular line that goes, "Slim THICK with your cute ass, i MIGHT buy you a NEW bag." Do you see what he did there, the upper case letters represent an emphasis in his cadence to give his voice change in volume thus giving it timbre and making the rap instrumental he is rapping on more catchy.