Some say nothing good comes out of Iowa except corn. Corn and corn-fed alt-country musicians, perhaps. Like the Nadas. The Iowa quartet represents all that is oddly pleasant and yet remotely forgettable about Middle America. But, damn — give credit where credit is due. The Nadas have survived a 10-year tenure of midgrade exposure and success by sheer force of will. They’ve released half a dozen records, toured extensively and received mention in a 2001 issue of Playboy as “The Best College Band You’ve Never Heard Of.” No wonder they’re so successful with the college crowds — their key publicity occupies the flip side of an airbrushed centerfold. But who knows? Maybe the band’s appeal isn’t limited to the 18-to-22-year-old-frat-dude market. Regardless, as long as drunk college kids can hold up their beers to heartfelt heartland dirges, the Nadas have nothing to worry about.