Writing such music isnt all that difficult - what you need is a large variety of styles that you are familliar with and a good, professional working schedule. I have seen mike portnoys drum video where he explains how they work - LTE for example is 90% jamming - some of the songs have been written within just a few hours. They encapsulate alot of standards just playes differently. The way he explains it, it becomes very visual and not realy difficult.