Harpist Arthur Williams is a blues minimalist. He can evoke a wide range of colors and textures using a limited array of runs, riffs, and melodies with subtle variations in timing and tone--and like his mentor Rice Miller, he can make a silence almost percussive, punctuating his squalls and trills with long periods of emptiness that throw the intensity of his tone and the fierceness of his attack into stark relief. Williams appeared with the late Frank Frost on his now classic 1966 album, Jelly Roll Blues, but not until 1999 did he cut his debut as a leader, Harpin' on It (Fedora). On his 2000 follow-up, Ain't Goin' Down, he takes on pop-blues standards like Willie Mabon's "Poison Ivy" and Ivory Joe Hunter's "Since I Met You Baby" as well as meatier fare like the venerable "See See Rider" and his own Delta-styled creations. He sounds out of his element on some of the poppier stuff, but on "Rider" he spins out saxlike lines that flex from deep-bent low notes to high, ragged squawks. The instrumental "Slop the Hogs" is a showpiece for his understated craftsmanship: he begins in a tremulous tone, then builds intensity, extending his warbles through several phrases at a time before breaking them up into short bursts punctuated by tongue stops. Toward the end he returns to longer lines, then signs off with a series of skitters up and down through the registers. And on the grinding "Arthur's Blues," between bouts of cracked but evocative singing, his solos dance impishly around the rhythm, coming in behind the beat or ahead of a phrase but always returning to the turnaround in time. Friday and Saturday, April 20 and 21, 9:30 PM, Rosa's Lounge, 3420 W. Armitage; 773-342-0452.