Todd Rundgren has never been at a loss for clever ideas, but even so, Space Force is a particularly ingenious project. Like its predecessor White Knight, it's a collaborative effort, but the catch is it consists entirely of songs the original composer left unfinished -- Rundgren stepped in to give them a final polish. It's not an uncommon way of working. Essentially, it's similar to the role of a producer who will come in and push an artist over the finish line, but with Space Force, it works in reverse: He solicited songwriters for their incomplete songs so he could bring them to life. Rundgren works with a couple of up-and-comers here, ranging from his indie descendants the Lemon Twigs to multimedia hip-hop artist Narcy, but he generally turns to old friends, colleagues, and like-minded stars for their own idiosyncratic scraps. The results are naturally a bit scattered sonically, as any record featuring Steve Vai and the Roots would inevitably be, yet it's tied together by Rundgren's aural aesthetic and sense of mischief. The latter comes into focus with "Down with the Ship," a novelty number spun out of a Rivers Cuomo track sampling the Skatalites's "Dick Tracy" that could easily have slid onto The Ever Popular Tortured Artist Effect, where it would happily coexist with "Bang the Drum All Day." A lot of the album shares a similar retro-futuristic vibe with Ever Popular while also echoing the post-psychedelic soul of A Wizard A True Star, an unexpected and happy development. This sense of indulgence does mean that Rundgren's impishness is dialed up to an extreme, surfacing on the absurd Sparks romp "Your Fandango" and "I'm Leaving," where the Lemon Twigs apparently gave Rundgren a song designed to sound like a cut buried on the forgotten side of the double-LP Todd. Cheap Trick's Rick Nielsen helps ratchet up the obnoxiousness with the wailing "STFU," while Thomas Dolby sounds uncannily like Roger Waters on "I'm Not Your Dog." All this sound and fury is good fun yet the heart of the album lies in lovely, ethereal moments like Adrian Belew's "Puzzle" and Neil Finn's "Artist in Residence," which both recall Utopia at their soft rock peak, and "Godiva Girl," where the Roots help ease Todd back into Philly soul mode.