Returning after a five-year gap (which, granted, included a box set and a collaborative record with Bonnie "Prince" Billy), Tortoise confronted a pair of age-old musical questions: does anyone really care about an experimental rock group after 15 years, and does said group actually have anything to say after that length of time? After all, the sound of rock's future circa 1994-1996 was beginning to sound tired by the time of 2004's It's All Around You, and the sense was growing that Tortoise should call it quits and begin accumulating enough years of inactivity to eventually be rediscovered, remastered, and reunited. Beacons of Ancestorship neatly squashes all those questions and assumptions, revealing a band that is just as fascinated with sound, just as intrigued by its myriad possibilities, and just as unerring in presenting those ideas in the form of entertaining instrumental music as when it debuted in 1993. The time signatures are constantly shifting, the lights of vitality and inventiveness Tortoise displayed 12 years earlier are completely undimmed, and the reference points for their music are constantly expanding (on tap here, among the dub and Krautrock and minimalism and jazz, is surprisingly abrasive punk for "Yinxianghechengqi"). The opener is eight minutes of bliss, wheeling and turning every few minutes, eventually leading to a great full-band jam that looks back to an earlier age of Chicago post-rock with a closing that's strikingly reminiscent of early Trans Am. The spaghetti Western impressionism of "The Fall of Seven Diamonds Plus One" would be perfect for their excellent TNT LP, and the group gets positively off the wall at the end, with a pair of songs ("Monument Six One Thousand" and "Charteroak Foundation") that pit guitar lines over drums-and-bass tracks that don't sound as if they were recorded for the same selection. It can be incredibly difficult for an experimental group to continue experimenting for years on end without getting stale, but Tortoise achieve that balance effortlessly.