Well, they were studio jams that were similar in some ways to the JATP on stage jams. Usually long selections with stars of the Granz stable combined. 1 and 2 were the great alto player jams (Hodges, Parker et al), 3 and 4 had Basie at the keys and players such as DeFranco and Getz and Gray and Smith and Jones, etc. Most of the really good guys that Granz produced had a turn here or there. As a body of work it's quite interesting and impressive. . . some volumes better than others of course, but I've been waiting for a nice package like this for some time!