Rap is all about great lyrics. The last few years became all about beats/bass. The formula is the same though, repetition over and over and over with catchy loops/samples. If you call that music, so be it. Overated.
All you need is a sequencer , a sample CD with few beats in there, a random melody that you can make with 1 finger without even knowing what you doing and a bass in a 4/4 sequence. There you are.