Anteroposterior diameter changes of the rib cage and abdomen were recorded during respiratory, speaking, and singing activities in six adult male subjects, all baritones with extensive classical singing training and performance experience. Data were charted to solve for lung volume, volume displacements of the rib cage and abdomen, and inferred muscular mechanisms. Separate major roles were inferred for different parts of the respiratory apparatus in the singing process. The abdomen served as a posturing element that mechanically tuned the diaphragm and rib cage to optimal configurations for performance. The rib cage operated as a pressure-flow generating element that regulated expiratory drive. And, the diaphragm functioned as an inspiratory element devoted to reinflating the lungs. Subjects' descriptions of how they thought they breathed during singing bore little correspondence to how they actually breathed. Implications for the training of singers are offered.