By the time London-based Helena Costas coos, "The voice of Merlin echoes through the moors," the fairy dust on her psych-folk debut is pretty thick. While she riffs on redwoods and rainbows over delicate acoustic guitar, collaborator Danger Mouse adds whimsical synth whirs, lava-lamp rhythmic burbles and even actual grooves. Like Alice's Wonderland, the world of Joker's Daughter is freakish and...