its a small excerpt of that piece.

from the ROTJ liner notes: Page 14: "Williams now delivers a satisfying musical pay-off to the Tattooine sequence, a bold action cue filled with familiar orchestrations of the Rebel Fanfare as the heroes unite in a battle against Jabba's bandits."
Page 19 "SAIL BARGE ASSAULT [alternate] is a straightforward action cue that was dropped when it was decided to use more of Luke's Theme and the Rebel Fanfare for the sequence."
Page 26: "Action music is heard as the shield generator explodes, with the Rebel Fanfare occurring as Lando finally leads the fighters toward the Death Star"