Say what you will about Herbie Hancock's controversial Grammy win, but there is no arguing with a man who steps onstage rocking a wireless keytar.

Buoyed by the plate-shifting bottom end of his jazz-funk classic "Chameleon" (carried by the powerhouse rhythm section of Vinnie Colaiuta and Marcus Miller), Herbie began his Yahoo! Live Set with the air of a giddy conquering hero, playing with such an undeniable sense of adventure and joy that all memories of his lovely but eyelid-fluttering "Joni Letters" were wiped away in a storm of actual, head-bobbing jazz.

Granted, when your back catalog includes classics such as "Cantaloupe Island," "Actual Proof" and the genre-crashing early MTV staple "Rockit," there's little chance of keeping a roof on any venue, even a vaguely production-oriented stage in Century City. Hancock even flexed his ability to stretch some boundaries by showcasing a reworked "Watermelon Man" that incorporated elements from his guitarist's (Lionel Loueke) time signature-melting composition "Seven Teens," which together sounded like an alien funk jam tumbling down a flight of stairs.

But the biggest ovation from the small, invite-only crowd came for who Hancock had hidden in the wings: Joni Mitchell.

Mitchell was dressed in a long, utterly insane but totally perfect dress bearing what could've been a scene from the Bhagavad Gita across the front, and her presence alone inspired a few audible gasps. While the set was missing the extra touch that her tiny, track-suited Jack Russell terrier brought to the rehearsal, Mitchell's three-song collaboration with Hancock's band revealed the biggest thing missing from the pianist's lauded tribute album: Mitchell herself.

The years may have taken the angelic lilt away from Mitchell's unmistakable voice, but the husky tone in its place added a new weight to "River," sounding like a slow-moving mix of molasses, honey and regret. Mitchell has always been closer in spirit to a jazz artist than her folk contemporaries, and Hancock proved her perfect foil as each instrument delicately lapped around the edges of her lyrics with a sound that was still true to the original, but constantly shifting and evolving. If only mainstream jazz as a whole could be so lucky.

(Yahoo! will air the Herbie Hancock / Joni Mitchell Live Set on April 1.)