The prog spectrum is an attempt to categorize the whole body of prog music in a meaningful way. Many of the categories are really broad and inclusive, some others are rather specific. The latter are included for historic reasons. Genres like RPI, Krautrock and Zeuhl are so well established that it simply would not make any sense to ignore them. The genres are listed in a particular order which attempts to make sense both in a chronological and stylistic way, grouping similar categories together. This only works to some extent of course, there is no perfect solution.
Below you see all of the prog spectrum categories with the top 12 releases of the user. The releases are chosen according to the tags the user assigned. You can see the full prog-spectrum for all users here.