Born from the ashes of Bulkhead and Turkish Delight, the Boston-based Betwixt pops up on the cultural radar with a frequency its predecessors never achieved: an NPR showcase here, a mention on MTV News there. Lead singer Leah Callahan was even featured in a Cosmo article about dating this past January. Despite its undeniable pop appeal, the quartet doesn’t fit the traditional corporate-friendly mold: The not-so-subtle goth overtones on 1998’s Moustache come courtesy of Callahan’s slithery, sexy voice (think Natalie Merchant meets Siouxsie Sioux) and cello-heavy songs about Anaï#s Nin, the number 13, and communing with the dead. So, which are they, dark and brooding or light and fluffy? Solve the debate when Betwixt opens for The (Last) Seconds (of) at 9:45 p.m. at the Galaxy Hut, 2711 Wilson Blvd., Arlington. Free. (703) 525-8646. (DA)