How to read a greneng

[Bjorn]

In another thread Alan made the following 2 remarks.

In short, the greneng is a mess, as it is, it does not carry any message at all.
The greneng is the big surprise to me:- it is correctly cut, the man who cut it knew what he was doing, but his level of knowledge was at pandai level, not mpu level. He has cut correct Mataram rondha, but has cut them poorly, and the complete greneng says less than it should.


This to me raises some questions. How should one read a greneng? What should the greneng express/say? And how has this expression changed according to region and time?