From ominous organ overtures to macabre piano melodies, keyboard instruments are an essential element in any spooky symphony. But foreboding as they might be, Ad Astra per Aspera's sinister synthesized sounds aren't quite as scary as the group's violent, dual-guitar eruptions or its Exorcist-style vocals. The group usually builds its chaotic crescendos without malice, but at its Halloween show, it might stretch its already extreme dynamics to dangerous levels -- perhaps dragging listeners' numbed brains from their ears with jagged hooks as though for mass mummification. Oh, and there will be costumes involved: Singer Mike Tuley promises "two helmets, three wigs, one sword, one fake mustache, one jumpsuit and one frilly pink tuxedo shirt," plus free cookies for everyone (seriously) and carved-pumpkin stage lighting. Opening act Dios probably gets a lot of hecklers requesting "Holy Diver," but maybe this time these guys will actually play it, because it's a holiday and all.