Natural auditory environments, be they cocktail parties or rain forests, contain many things that concurrently make sounds. The cocktail party problem is the task of hearing a sound of interest, often a speech signal, in this sort of complex auditory setting (Figure 1). The problem is intrinsically quite difficult, and there has been longstanding interest in how humans manage to solve it. The problem is not unique to humans, however—many other species confront something similar. Nonhuman animals frequently must identify mates, offspring, or adversaries in crowded environments containing many animals vocalizing at once. Many species of frogs, for instance, must use conspecific vocalizations to locate mates at night, when there are few visual cues, amid hundreds of other frogs.