It's hard to say which is more arresting in Imogen Heap's music: her finely crafted pop songwriting or her intricate, high-tech production. Together, they make for an irresistible package. “Come Here Boy,” from her 1998 debut album, wraps her powerhouse voice around inventive production that fuses Lilith Fair pianos with big beat's drum breaks; “The Happy Song” applies hyperkinetic sound design to what's essentially a nursery rhyme. Even more head-spinning is 2005's “Hide and Seek,” a deeply moving, wildly vocoded a cappella performance that anticipates Bon Iver's digital turn by six years.