Secondstar, Heidi Sidelinker and Third Wheel Band (in the picture) are among the 13 acts playing tonight at the free Deli-sponsored 5th Annual LC Fest, organized by independent music community Local Correspondents at Bar4 in Park Slope. Secondstar plays folk-pop that veers from bright and shiny to dark and melodic, while Heidi Sidelinker’s solo work as a singer/songwriter (she’ll also perform tonight with her band Lowry) combines wistful, lilting tunes with sweetly melancholic acoustic underpinnings. The Third Wheel Band is an American roots group combining influences as varied as bluegrass, country, folk, talking blues, early jazz and rock ‘n’ roll. Their debut album On Willow Street was released in November 2010. For the complete schedule of performers for the entire festival (doors open at 7 p.m., music starts at 8 p.m., through May 22nd), visit the LC website.