Norah Jones at the Tower Theater

Norah Jones isn't known for delivering shocks, or even more than mild surprise; any attempt to discuss her body of work should begin by opening the nearest thesaurus to the entry for pleasant.

But it was at least a trifle unexpected to see the mellifluous singer Saturday night at the Tower Theater standing at center stage with a cherry-red Fender guitar slung over her shoulder as her five-piece band swung into "I Wouldn't Need You," the first of seven straight songs from her fourth album, The Fall.

Although the description was never a tight fit, Jones' 2002 debut, Come Away With Me, introduced her as a piano-playing jazz chanteuse. Aficionados scoffed, deriding her music as aural wallpaper for bourgeois suburbanites, but the album went on to sell more than 22 million copies worldwide, a phenomenal number then and all but unthinkable now.

That amount of public affirmation is a powerful enticement to tread water, and Jones' musical evolution has been on the narrow side of incremental.

But The Fall breaks decisively, if not jarringly, with her past, including former boyfriend Lee Alexander, whose sound and songwriting were instrumental to Jones' initial success.

That Jones is eager to move on can be inferred from the evening's set list, which overwhelmingly favored songs from the new album - all of them, in fact.

"It's Gonna Be" built on a distorted organ riff out of 1960s funk, while the keyboards in "Chasing Pirates" echoed and died away gently, like waves receding into the distance.

With its leisurely shuffle beat and delicately plucked chords, the post-breakup lament "Back to Manhattan" was a fitting stylistic throwback, but even there, Jones' brushed-snare voice sounded heavy with loss. "Sinkin' Soon" added a dash of Brecht-Weill debauchery, sounding more like Tom Waits than her sleepy version of Waits' "Long Way Home."

Jones' songs have always run toward melancholy, enough that the lighthearted "Sunrise" was singled out as a "happy song." But her presence on stage was uniformly upbeat, as if even she couldn't maintain a wistful demeanor when confronted with the smooth beauty of her songs. A little more roughness, in fact, would have been welcome, something to suggest more complicated textures under the songs' burnished exteriors.

But Jones skimmed ever forward, always progressing if never breaking the surface.