THE ALBUMS: SUPERTRAMP: "Paris," A&M SP-6702; Joni MITCHELL: "Shadows and Light," Asylum BB-704.

Live albums are the pax in bello of rock: Musicians get to take a break from the studio/tour/studio merry-go-round, while the fans usually give their wallets a rest and wait for the next studio blitz. Such LPs tend toward redundancy and slap-dash sound quality, and are best heard on a car radio.

That said, two current exceptions, Supertramp's "Paris" and Joni Mitchell's "Shadows and Light," may not prove the rule so much as blow it out of the trenches.

Recorded lovingly at the Paris Pavillon, "Paris" makes it clear that a wealth of good material preceded "Breadfast in America," the 1979 album that put Supertramp over the top commercially. Not only are we (and they) spared a rehash of "Breakfast" (only three of its songs appear here), but each song in this collection has been altered in some way from its original version.

The result is a fresh vision of the combination of pure rock technique, songwriting skill and canny humor that makes Supertramp such a sophisticated and engaging band. "Crime of the Century" forfeits none of its brooding power in this context, and "Bloody Well Right" becomes a foot-stomping tour de force. Only "The Logical Song" loses punch, taken here at too fast a clip. But overall, "Paris" demands repeated play, especially at a respectable decible level.

If Supertramp has made some deft alterations for the sake of variety, Joni Mitchell has performed laser surgery on some of her earlier works, and the result is nothing short of a miracle. Gone is the dogmatic feminism that weakened the pulse of "Don Juan's Reckless Daughter," gone the nervous meandering that jaundiced her foray into jazz.

For "Shadows and Light," Mitchell has assembled her most formidable lineup to date: Jaco Pastorius on bass, Don Alias on percussion, Pat Metheny on lead, Michael Brecker on sax and The Persuasions, for heaven's sake, on backing vocals.

But unlike "Mingus," this is not some showy collision of styles. Somewhere along the way, Mitchell has discovered her jazz chops, and the ensemble performance here is as clean and tight as a baby's fist.

Pastorius' indelible bass signature scrawls humor into "Edith and the Kingpin," goosing the group into a four-bar disco drone when Mitchell sings "The band sounds like typewriters." On "Free Man in Paris," Brecker draws the blinds on dark sentimentality with a break so bright you need sunshades. Alias digs deep into the jazz soil of "Dreamland" to reap the African roots of a field holler. And Metheny's work throughout this album has a satiny, flowing jazz feel.

But the most pointed example of tasteful interpretation is found on the title cut. Whereas the original version of "Shadows and Light" (on "Hissing of Summer Lawns") had the structure of a Gregorian chant or kyrie, Mitchell and the Persuasions carry it to its logical gospel extension, and the result is righteous. "Hostage smiles on presidents/Freedom scribbled in the subway," sings Mitchell with a soulful irony absent from the 1975 version. "It's like night, night and day." s

And in "Woodstock," which Mitchell wrote in an era when things seemed so black-and-white, she implores us to get ourselves back, if not to the garden, to "some semblance of a garden." That's just one indication that she's discovered a little gray in the heart of the jazz night.