Kuda Kepang


See this amazing article with lots of pictures and videos about Kuda Kepang, the Javanese horse dance which involves trance and possession:


Does anyone know what are the spiritual theories behind the dance?  How often is it performed and where can I find out more about it?  I am refering to those performances that involve trance, not the tourist/cultural festival variety. 

I wonder if there is a connection in the use of bomoh/medium and trance for Southeast Asian cultures such as Hokkien Taoism and traditional/pre-Islamic Malay beliefs.