ABSTRACT: Cooperative behaviors require precise coordination of learned movements between individuals. To achieve these performances, brain circuits in each participant integrates information from at least two sources, feedback from the animals own behavior and information from the partner. How the brain represents these categories of information for the production of cooperative behaviors is currently not known in any species. In order to understand how the nervous system controls a cooperative behavior, we characterized both the behavior and neural activity of a bird whose song is a precisely timed duet between males and females, the plain-tailed wren (Mann et al., 2006). These birds live in thick bamboo on the slopes of the Andes. Behaviorally we hypothesized that each participate would sing its part as a fixed-action pattern or based on constant auditory feedback from the partner. To examine this we compared naturally occurring duet singing to solo singing and found that each bird does not sing in a stereotyped fixed-action pattern. To understand the neural basis of the behavior we recorded neural activity from HVC, an area known to be necessary for learned song production. We found that HVC responded best to auditory playback of duet song and, that both males and females responded best to solo female song. These neural responses suggest an evolutionary specialization for a cooperative behavior in duetting birds.