Staged, as opposed to informal or impromptu, jam sessions were all the rage in the early ’50s because they promised audiences juiced with post-war affluence more all-stars for the buck, more bounce to the ounce . . . more, more, more. The Donald Trump of the jam was Norman Granz, who, in addition to crisscrossing America with his Jazz at the Philharmonic, thrived on horn-to-horn combat in the studio. The nine studio jams Granz produced from ’52 to ’54 have been collected in a smartly designed cube, and the music holds up better than you might assume. The sessions dominated by swashbucklers Roy Eldridge, Dizzy Gillespie, Lionel Hampton, and Illinois Jacquet yield the expected pandemonium, with some tempos too fast for anybody’s good. But smitten with Lester Young and paced by Count Basie, Stan Getz and Wardell Gray cross swords only to prove who can be more subtle. Taking his sweet time, Benny Carter walks away with top honors in a confrontation with Johnny Hodges and Charlie Parker. Ben Webster is luminous on the ballad medleys, and where else are you going to hear Charlie Shavers and Willie Smith in top form during this period? It’s too bad neither Tatum nor Young himself entered the competition, and even more of a shame that the series was discontinued before Jimmy Giuffre and Lee Konitz joined Granz’s roster, because they might have brought a greater element of shading to the romps. But what’s here is rich, however uneven.