Songbirds have been used widely as model organism for neuroscientists studying complex sequential behaviors and sensory-motor learning. Like human language, acquisition of singing behavior requires certain amount of learning and training in juvenile stage. This review paper focuses on (1) the existence of specialized neuronal circuits for singing behavior and (2) the mechanisms by which neural circuits generate song sequences. Especially, the contributions of NIf, an auditory relay nucleus, are introduced based on biological data and our recent model studies. These findings shall be used in model studies which elucidate some of the most fundamental questions in neuroscience.