Previously, we have discovered that vocalizations of Xenopus are produced by central pattern generators, neural circuits that produce rhythmic outputs in the absence of rhythmic input, contained in the brainstem. Although we have been able to identify the activity patterns of a few types of vocal neurons, it is essential to characterize the activity of all the neurons to understand how the nervous system generates vocal behavior. Using recently developed Neuropixels probes, we have recently begun to obtain recordings from hundreds of neurons simultaneously during calling. Our goal is to identify how different aspects of calling including initiation, phase transition, and termination are coded by single neurons and a population of neurons.