When it comes to diversity, pop music puts the Reform Party to shame: For a brief time, the would-be reformers included Jesse Ventura, Warren Beatty, Pat Buchanan, Ross Perot, and more. But pop as a genre is arguably more diverse, a definition broad enough to accommodate the fey sensitivity of Belle And Sebastian, the airy deliberation of Low, the overdriven anthemics of Fountains Of Wayne, the ornate retro reverence of the Elephant 6 collective, and the saccharine sweetness of a hundred boy bands. That's saying nothing of the thousands of acts defined by a genre with the word "pop" attached to it, or of the generations of players and styles that preceded today's. In other words, countless musicians play pop, but not many effectively mix and match its many definitions. Seattle's increasingly outstanding Death Cab For Cutie pulls it off better than most on the marvelous new We Have The Facts And We're Voting Yes, seamlessly incorporating gorgeous ballads ("Title Track"), too-hooky-to-be-true radio anthems ("For What Reason"), and material that's positively rocking ("Company Calls"). We Have The Facts just gets better the longer you listen to it, improving over its predecessor at every turn and revealing a surprising mastery of pop's many languages. A great pop band not so renowned for its diversity (if known at all) is the D.C. outfit Aden, which has quietly put together a nice little catalog of sweet, sensitive, understated music. Last year's Black Cow more than made the most of its limited palette, parlaying its limitations into a masterpiece of gently hooky stylistic consistency. With two- to three-minute songs built around barren instrumental frames—only the gorgeously clear guitar lines stand out—each song on Black Cow is dominated by Jeff Gramm's sweet, sensitive vocal phrasings. The new Hey 19 (the second album Aden has named after a Steely Dan song) often falls back on that effective formula, but finds the group stretching it in subtle and welcome ways. "Gulf Coast League" threatens to drift away on its own fluffy sonic cloud, but elsewhere Hey 19 actually finds Aden threatening to rock, particularly on an uncharacteristically distorted cover of Nice's "Dear John." Tonally consistent, lyrically evocative, and more musically creative than its predecessors would lead you to expect, Hey 19 only enhances Aden's status as an unduly hidden treasure. (Barsuk Records, P.O. Box 31016, Seattle, WA 98103; Teenbeat Records, P.O. Box 390898, Cambridge, MA 02139)