Here are two musical styles that at first blush might not seem to go together: Staple Singers and AC/DC…the Aussie hard rock group. But St. Louis artist Nikki Hill seems to pull it off. Just a couple of years ago, Hill was working as a bartender and a personal trainer when her guitar-playing husband implored her to step out from behind the bar and in front of the mic. Since then the two Hills and the rest of the band have been touring non-stop, winning converts with a voice that’s been called “as sweet and luscious as it is gritty and raw.” Her new album “Heavy Hearts, Hard Fists” was released last week. The play a show Friday at Fitzgerald’s in Berwyn, but they stopped by the Morning Shift to give us a preview.