Supermarkets are for shopping, not singing. Right? But Amy Pickard and Beth Case, the two transplanted Southerners of She-Haw are having a particularly good time playing at Fresh Fields during a Habitat for Humanity benefit. "This one's for aisle number seven," announces Pickard into the PA as the two break into a roots-folk rendition of Bad Company's "Feel Like Making Love." Their stylistic changes are so precise, so dead on, it takes a few lines to place the song as a classic rocker. Their voices—Pickard's high alto, Case's smooth near-tenor—blur into haunting harmonies. The British rocker sounds like it was written for two women and an acoustic guitar.

Most of She-Haw's influences come from the Southern folk tradition ("Bad Company's from Southern England," jokes Case later; Pickard rolls her eyes).

The two have been playing together since they met four years ago at Case's wedding, though they've only been playing out since February at parties and places like the Lionfish coffeeshop and the Kumquat performance space. Their sound is spare, just Pickard picking and strumming on guitar and Case playing percussive instruments like a wood-bead purse and a Ugandan instrument (it looks like a sushi roller) that she uses as a washboard/rattler. Most impressive is the way their voices combine, dancing effortlessly in and out of each other's melodies. It's early country mixed with traditional folk and bluegrass with contemporary singer/songwriter intimacy.

Listing favorites like the Carter Family, Loretta Lynn, the McKinney Sisters (who played with Bob Wills and his Texas Playboys), Hank Williams Sr. and the Sons of the Pioneers, the duo's Southern/Appalachian roots are evident, though neither speaks with a pronounced twang. Pickard, 25, moved to Philly from Tennessee to attend Penn and now teaches GED classes. Case, 31 ("I'm the Minnie Pearl of the group," she explains. "I'm the Ernest Tubb," counters Pickard), is a Texas native who lived in Tennessee briefly before moving north in 1991. She's a costume designer and responsible for the duo's matching outfits—today they're wearing their "Sunday-go-to-meeting dresses."

"There's a tradition in country music to dress up, to put on a show," explains Pickard. "It's like a Dean and Frank thing… but they're more schmaltzy," says Case.

The name, as Case explains, was "a happy accident. We were just sitting around and we had He Maw, but that just didn't sound right." "We did every permutation of He Maw until we came up with She-Haw," jokes Pickard.

Right now the majority of their set is covers, but not cover-band dreck—songs like the traditional "Tennessee Waltz" and "Oh Death," the Carter Family's "I'll Be All Smiles Tonight," Connie Francis' "Many Tears Ago" and the yodel-ly "T for Texas" as done by Williams and Wills. Their most striking number is the Stan Jones-penned "Ghost Riders In The Sky": Pickard sings the eerie lead over Case's dust-blown ghost howls.

"It's a sisterly thing," continues Pickard. "We like to keep it open, keep it fun. We bicker on stage, but we always kiss after the show… not a French kiss or anything, though."