CAMBRIDGE -- For such an unassuming performance area, the makeshift stage set up in Harvard Square on Sunday afternoon carried a lot of weight on its shoulders. Serving two masters, it provided entertainment for the afternoon's Oktoberfest while also being a part of the NEMO Music Showcase, which had been going on all weekend. Unlike other NEMO venues, the Harvard stage was free, which, combined with the activities on the streets of the square, all but guaranteed a transitory audience.
That seemed to be the case by mid-afternoon, as turntablist DJC filled the square with M.I.A., Dr. Dre, and plenty of polkas layered with hip-hop and techno beats. He alternated with laptop artist Wayne and Wax, who displayed a particular fondness for mashing up Cars songs with rhythm tracks such as Run-DMC's version of ''Walk This Way" and K7's ''Come Baby Come," but some beat-matching problems and the crew setting up the stage for Grace Potter and the Nocturnals' upcoming set suggested that the two were simply filling time.
Not so for the Vermont-based Potter, who was like Susan Tedeschi if she had been wrecked by gospel soul and Little Feat instead of pure blues. While she was unable to stop pedestrian traffic completely, she slowed it to a trickle with an outsize, soulful moan that was equally effective in her controlled and quiet moments as it was when she was wailing at full power. She and her band finished by tearing through the fast, funky ''Nothing but the Water," which ended with what could have been an age-old spiritual accompanied only by Potter's tambourine before she walked off the stage, still singing.
With guitarist Sam Jayne admitting, ''We're not used to daylight," Love As Laughter took the final slot of the day. Starting with thumping drums and a guitar balanced between a scraping drone and pure noise, the New York band's songs ranged from the deep bass of Sabbath-y riffers to the singsong ''I Won't Hurt You," in which an almost childlike innocence, like that of the Velvet Underground's ''I'm Sticking With You" and the White Stripes' ''We're Going to Be Friends," was punctuated by proclamatory guitar/drum explosions. By then, the crowd was back to sampling mode, with a small group of loyalists sticking around to hear songs such as the punky ''Temptation Island" and ''Every Midnight Song."