BOB DYLAN AND JONI MITCHELL. Two of pop's most uncompromising icons still have fire in their loins. Seen Sunday at Madison Square Garden.

NEARLY A quarter-century has passed since Bob Dylan and Joni Mitchell last performed on the same bill at Madison Square Garden, and given the vicissitudes of both artists' careers, their Sunday night double-header could have been a double-downer.

But in dramatically different sets, the two pillars of the singer-songwriter genre, who years ago dared to plug in and eschew the folk label, demonstrated they have far more to rest on than their laurels.

Although both sets were heavy on old favorites (Mitchell opened solo with a swinging "Big Yellow Taxi," Dylan roared with his twangy, four-man band down "Highway 61"), both artists had their way with melodies and arrangements, masterfully restyling them to make them fresh.

For Mitchell, this meant applying the swirling, muted, sophisticated jazz shadings that have been at the heart of her more recent material. Dylan's flawless maneuvers ranged from bluegrass to rock-country rave-ups to bluesy shuffles.

Both artists relished the spotlight. The radiant Mitchell, 54, was far more animated and polished than during her performance in August at the site of the original Woodstock music fest. She joked frequently with the crowd and even attempted a nasal Dylan imitation.

Dylan, 57, who has been prone to moping and mumbling onstage, was almost dotty as he grinned, danced and struck mock rock poses with his guitar. Perhaps not coincidentally, that charismatic playfulness has marked his performances since the release last year of his latest album, "Time Out of Mind," his gloomiest and most morbid LP.

Mitchell's voice, once impossibly high and clear, has turned husky, giving her new depth and allowing her to tackle styles that once she would have rendered too ethereal. Despite her stilted use of a cigarette as a prop, her torchy cover of Ira Gershwin's "Comes Love" positively smoldered.

Her guitar picking, over unusual tunings, also has grown more sophisticated, breaking into surprise rhythm changes and succinct bursts. The deft touches of her jazzy, four-piece band enhanced the contemplative mood.

She played only one tune from her new album, "Taming the Tiger," a song about ardent lovers titled "The Crazy Cries of Love." Recorded, it's among the release's weaker tracks; live, it was a warm, inviting dream fueled by Greg Leisz' floating pedal steel and Chris Botti's velvety trumpet obbligato.

Dylan, who is riding his biggest popularity wave in years, delivered a raucous "Rainy Day Women #12 and 35," a poignant "Blowin' in the Wind," and a riveting, acoustic "Tangled Up in Blue" that was as jangly and rowdy as his first electric shows in '65-'66.

His lone curve ball was an almost deadpan cover of the sentimental ballad "Times We've Known" by French crooner Charles Aznavour who, Dylan inscrutably reminded the crowd, is performing in Manhattan.

Of Dylan's new tunes, "To Make You Feel My Love" was tepid, but he reshaped "I Can't Wait" into a snappy, funk-meets-country rocker. The gloom of "Love Sick" was belied by his smile - an unknown commodity even a few years ago.

"It's like he's got a whole new lease on life," gushed a pert blonde who'd last seen him at the Tilles Center in 1990. Ah, but he was so much older then; he's younger than that now.