Karen O has always had a thriving career outside of the Yeah Yeah Yeahs. Most notably, her collaborations with Spike Jonze -- the Grammy-nominated music for 2009's Where the Wild Things Are and the Oscar-nominated "The Moon Song" from 2013's Her -- revealed her as a thoughtful solo artist with a range that went beyond her band's already eclectic music. While her official debut album, Crush Songs, a collection of lo-fi songs dating back to 2006, is far from showy, it continues in this witty, heartfelt, largely acoustic vein. There's a wonder and intimacy to the album that reaffirms why her music for Jonze's movies is so affecting; tracks such as "Ooo" and "King," a lullaby inspired by Michael Jackson, share that bittersweet whimsy. This playfulness extends to Crush Songs' deceptively simple arrangements. "Visits" boasts a rudimentary mechanical beat that sounds like a particularly rhythmic game of ping-pong, while "Body"'s percussion comes from clicking mouth noises that evoke wood blocks. O wrote Crush Songs when she felt like she might never love again, and its impressionistic glimpses, fragmented memories, and daydreams are more about possibilities than committing. The album's hissy sound quality underscores this tentative emotional state, and the shorter songs teeter between raw feelings and feeling unresolved; "Comes the Night" never quite coalesces, but "NYC Baby" captures yearning in just under a minute, and "Sunset Sun" is such a vivid portrait of a summer night, you can practically hear the crickets chirping. Not surprisingly, the album's more fully formed songs rival her previously released solo work. "Rapt" maintains Crush Songs' shy sweetness even as O puzzles over her tumbling emotions ("Love is soft/Love's a fucking bitch"); the chugging "Day Go By" could be an unplugged Yeah Yeah Yeahs song, and "Beast" distills the hopeless side of crushes in its eerie, timeless melody and veils of distorted backing vocals. Given that much of her previously released solo work is more accessible and more ambitious than this set, Crush Songs is a slightly strange choice for O's first full-fledged solo effort. Still, this unassuming musical diary showcases many of the best things about the music she makes on her own.