The label ceased with CDR's after using them for 5 and 6 (ironically, these two volumes are IMO the best), so all subsequent volumes are on pressed CD's. I assume MIG got a lot of flack for the CDR's. Their response to my query was they wanted the discs to look like vinyl records as the reason for CDR's, which is dumb as the label surfaces look like vinyl records anyway. Also, Schulze's manager, Klaus D. Mueller, who is a cantankerous little prick, argued with me back and forth that they were not CDR's, but real CD's!!
Jesse, beware 1 & 2 are pretty minimal and strange. There are some good tracks, but overall the music is very experimental and not the "big sound" of his '75-'77 heyday. As for 9-12: I bought 9-11 and didn't care for 9-10 at all, but I liked 11, which is pretty damn good early 90's music (think it's from 1993) in the vein of the Dark Side of the Moog series on Fax, with long symphonic passages. Actually the only ones I've kept in my collection are volumes 5, 6, and 11 (if that tells you anything), as many of the volumes either have poor sound quality (recordings from bootlegs) or are heavy on the cheesy new wave 80's sound he had.
Volume 12 just came out and most likely I'll buy it, but want to hear some samples first...