To make this approach work, the placid passages must be mesmerizing enough to lull listeners into false security, and the jarring bursts must be so intense that their aftershocks keep pulses racing during the expository instrumental segments. In the past the Mars Volta has bungled this balance, either administering adrenaline overdoses or inducing terminal boredom. Frances the Mute, though, makes glacial momentum shifts compelling, mostly because the payoffs pack Titanic-meets-iceberg impact. The traditional song segments hiding in these sprawling four-part suites recall Talking Heads' polyrhythmic punk tribalism and Led Zeppelin's epic arena-size mysticism. Like King Crimson, its clearest progressive progenitor, the Mars Volta embraces symphonic string arrangements, slow-winding guitar squiggles, lost-in-the-mix choral accents and spasmodic signatures. But whereas '70s art-rockers aligned themselves with classical literature, the Mars Volta makes its own mythology. Its inscrutable bilingual lyric sheet offers no easy interpretation of its inspirations, which only enhances the experience. True terror always comes from what's not shown.