It’s not just the heat that’s sizzling this summer. You’ll find the sizzle, too, in Invisible Theatre’s summer cabaret series, Sizzling Summer Sounds. Eight different shows stretched over three weeks make up the series, and they each promise a triple treat — acting, dance and music, says Susan Claassen , the managing artistic director of The Invisible Theatre and director and producer of the series. Audience members “should expect the unexpected in glorious talent,” says Claassen. The music touches on different genres and generations, with tunes that ranges from ragtime to Carole King. And don’t expect an evening of background sounds. “The music is the highlight, it’s not a sidebar to conversation,” Classen says. This year marks the series’ 25th anniversary, and in celebration some of the original performers from the premiere of Sizzling Summer Sounds are coming back to open the series in “The Borscht Belt Boys and Girl — The Sequel,” featuring veterans of IT’s ca...