Brad Mehldau did an exceptional job of keeping his stellar trio together for seven years, as proven by his fine Art of the Trio dates and 2004's Anything Goes.

But Jorge Rossy, the group's drummer, began spending more and more time away from music and at his home in Spain.

Mehldau, who is almost prolific in his recording process, recruited drummer Jeff Ballard to replace Rossy on Day Is Done.

Ballard has worked off and on with bassist Larry Grenadier in the trio Fly with saxman Mark Turner, so he's not a total stranger to the process.

Yet Ballard is a different kind of drummer, more diverse and certainly more kinetic in his approach, as evidenced by this disc.

This is Mehldau's most energetic and rigorous recording to date.

These ten cuts are comprised mainly of covers, though aside from "Alfie," there isn't anything here approaching a standard.

There are tunes here by the Beatles ("She's Leaving Home" and a glorious solo version of "Martha My Dear" with a Scarlatti-esque study in counterpoint to usher it in), Paul Simon (a jaunty read of "50 Ways to Leave Your Lover"), Nick Drake (the title cut), and even Radiohead (in the crackling energy of "Knives Out").

There are two fine originals as well: the shimmering "Artis," with its striated right-hand work, and the Latin-tinged "Turtle Town," a somewhat breezy ballad that is nonetheless knotty and off-kilter enough in its melody and in Mehldau's solo to become complex and challenging.

Day Is Done is another exceptional chapter in the Mehldau catalog, one that showcases a willingness to stretch itself to the breaking point and open up the band to a wider array of approaches.