When it comes to cosmopolitan country music, The Great Unknown are a reliable local source, making mellow moves these past few years to Jordan “Tuck” Burger’s emphatic midtempo drumbeats and ringing out the three-part harmonies with lead singer and songwriter Todd Henkin at the center. The Philly four-piece’s new album, So Strange and Loud, blows its sound open into something more lush and expansive, big on the crescendos and shout-out-loud refrains. Before, they might have been Philly’s answer to The Band (for those who didn’t already consider Dr. Dog such); now, they could be (dare I say it?) our own Dawes. Their Key Studio Session, recorded in the round last week, kept things relative downtempo and contemplative, in classic Great Unknown style, but just you wait till they open for Man Man at the 2nd Street Festival this Sunday; Henkin promises electric guitars, organs, amps and a whole lot of energy.