Suddenly, both men -- as well as a cake topped with burning candles -- disappeared inside an enormous cloud that moved in from stage right. The episode seemed briefly as though it might escalate into a replay of a notorious gig at this spring's South by Southwest conference in which the rapper and his crew leapt into the audience after being pelted with a beer can. So at the Palladium he and Schoolboy Q (of Lamar's Black Hippy group) retreated backstage for less than a minute, then returned once the air had cleared to finish the concert. He was offering reconciliation in the form of Schoolboy Q's "Hands on the Wheel," which begins, "Life for me is just weed and brews," and the capacity crowd happily accepted. "Peso" was sharp and plush at the same time, while "Kissin" Pink" summoned the medicated wooziness of Houston's so-called chopped-and-screwed scene. "Black Man," in particular, felt like a beam of focused intensity, as did another song with an unprintable title that featured the wily Detroit rapper Danny Brown, who also performed on Friday. He seemed equally adrift in a series of prerecorded voiceovers -- set to Vietnam-era pop songs and the slicing sound of helicopter blades -- about fighting a war to be understood; the concept remained elusive and out of reach. These moments felt especially weak compared to the electricity Lamar channeled in a guest appearance during Schoolboy Q's opening set. Wearing an all-leather outfit that Schoolboy Q likened to Martin Lawrence's in "You So Crazy," Lamar ripped through the first half of his song "Backseat Freestyle" with the kind of live-wire energy that demands attention. Then again, Lamar's job on Friday was easy: a minute or two of music, essentially, at the end of a week in which the release of his album dominated music news. He was there to prove that where there's smoke there's fire. Natina Reed dies at 32 Gary Clark Jr. plays every shade of the blues