If the commercial constraints of genre and chronic Hollywood sequelitis threaten to musically straitjacket even a legend like John Williams, the veteran playfully rebuffs such cynicism in his rich, mirthful score for this third chapter of the Harry Potter cycle. Whether inspired by a willful desire not to repeat himself, the continued reinvention of his jazz roots that brightened his scores for Spielberg's Catch Me If You Can and The Terminal, or the story's requirement for a handful of fresh themes, Williams informs his work here with an often dizzying range. The warm mysticism of "Hedwig's Theme" and classical farrago of "Aunt Marge's Waltz" can scarcely prepare one for the swinging, off-kilter "Knight Bus," a romp that suggests a head-on collision between the big-band bombast of1941 and the loopy, Cantina Band kitsch of Star Wars. From there Williams skips back a half-millennium or so for inspiration, conjuring the ancient children's chorus "Double Trouble" (its text adapted from no less than MacBeth), a medieval theme that becomes one of the score's inspirational foundations. Those with a taste for the composer's patent orchestral thunder won't be disappointed either, as the Herrmann-influenced percussion/brass bombast of "Buckbeat's Flight" and "The Whomping Willow.." attest with rousing zeal. It's arguably Williams' best Potter score to date, a soundtrack whose inspirations sprawl across six centuries -- and as many disparate musical styles. Enhanced CD features include a photo gallery and exclusive computer wallpaper and screensaver files. -- Jerry McCulley