When Chicago-based, Philly-born trio The Jai-Alai Savant delivers on its dub-heavy reggae-rock promise, Bass Delegate storms. “The Low Frequent See,” with its dark, late-era Specials vibe, and “Murder ‘Pon the Dancehall,” a prototype of dancehall punk, could be lectures to burgeoning dub-rock bands: Step one-learn these rhythms. But for much of Bass Delegate, Jai-Alai comes across as a regular-if particularly propellant and subtle-pop-infused punk rock band. The finest moments are when these faces meet in the middle: The XTC-ish “Sugar Free,” all pastoral harmonies and lurching pop-reggae rhythms, is nearly perfect.