Some sisters fight and compete with one another, some sisters lift each other up in supporting love, and still other sisters form girl groups and sing together for their enjoyment and yours. This last kind of sister group, the most entertaining kind, is what the Irving Sisters evoke. Although Elise LaBarge, Linden Christ and Sarah Simmons aren't sisters in the familial sense, you'll forget that detail as they harmonize and sing old favorites, such as "Mr. Sandman," "Boogie Woogie Bugle Boy" and other '30s and '40s tunes, as well as share stories about the artists who made these songs American gems. The Irving Sisters perform at at 7:30 p.m. tonight at the Kranzberg Arts Center Studio (501 North Grand Boulevard; www.irvingsisters.com). Admission is $20, cash only.