As a light but erudite experiment in faux biography, Woody Allen's Sweet and Lowdown appears to be sweet and fancifula gift for the love-him-hate-him crowd that enjoyed his nice movie Bullets Over Broadway a lot more than his nasty movie Deconstructing Harry. The subject purports to be Emmet Ray (Sean Penn), a fictional jazz guitarist famous during Allen's beloved swing-time 1930s as ''the second greatest jazz guitarist in the world'' next to the real Gypsy musical legend Django Reinhardt, but now faded into obscurity. And with a swipe (as he did in Zelig) at every documentary that has ever spliced comments from talking heads between spools of historical footage, Sweet and Lowdown calls on ''experts'' (including real jazz scholar Nat Hentoff and Allen himself) to deconstruct the shenanigans of Ray, who was undeniably gifted, but also undeniably a handful: The cat was egotistical but neurotically obsessed with Reinhardt, often drunk, outrageously unreliable, and generally awful around other human beings, especially women. Hattie (Samantha Morton), the laundress who loved him best, was unpretentious, unsophisticated, sexually robust, utterly devoted, and mute, and Ray treated her like a slipper.
With that good taste and vampirish lust he has for celebrity casting, Allen draws a snappy, loose-limbed performance from Penn, the perfect tantrum-throwing talent, twitching and squinting through cigarette smoke as he noodles Ray's favorite tune, ''I'm Forever Blowing Bubbles.'' (In fact, guitarist Howard Alden makes Ray's music; the whole soundtrack, arranged by Dick Hyman, is divine.) And in the consistently superb Morton, the director findsheaven help hera new muse, radiant and vulnerably funny-sad in the Giulietta Masina manner of all his best girls. (Fashionable starlets Uma Thurman and Gretchen Mol play better-dressed sweethearts.)
But as with even Allen's sweetest and most fanciful films, Sweet and Lowdown vibrates madly with charged autobiographical ions. This second-greatest-artist-who-worships-Django, created by the director who worships Ingmar Bergman, is praised in the end as a complicated genius whose mature work is his best; this exasperating music maker, with his untidy personal life, is absolved for being true to himself.
And may I repeat, the woman Ray loves truest is an enthralled mute who's as simply satisfied as an adopted child, demanding nothing more than a sandwich and a shred of attention? Soon-Yi, honey, Morton carries off the premise because she's capable of wordless eloquence, but for pity's sake, don't let your husband get away with all that jazz. B+