We love them from the day before yesterday, as in Forever Plaid or All Shook Up. And we love them before living memory, as in Tintypes. Old songs from the great deep river of American popular music are an inexhaustible resource. If there are a million songs out there (2 million? 5 million?), that’s more than enough to fill a thousand stage shows bringing them back to life, snapping their fingers and kicking up their heels. It’s just a matter of building the right package. And Roger Bean, creator of The Andrews Brothers, has the right frame: It’s a show about putting on a show.Dudes look like ladies: Counterclockwise from lower left, Gordon Maniskas, Andrew K. Moss, Sean Riley and Lara Hayhurst in Cortland Repertory’s The Andrews Brothers.