I think he is just exploring rhythms and sounds but would like to learn more. My other theory is that it just gives great satisfaction to be able to appear authoritative when he doesn't have a full answer, as he frequently rattles off beautifully rhythmic made up names in circumstances when he doesn't know the correct ones (eg talking about other children at the playground).
Any assistance in understanding or pointing to further information sources would be gratefully received. Its quite lovely, so I am not concerned, simply curious.