This study investigates the importance of the physiological domain in voice transformation. Voice transformation is defined as the process of modifying the voice quality of sentence-level speech while maintaining the same phonetic content. Transformation occurs as a function of gender, age, emotional state, disordered state, or impersonation. The basic question is: relative to pure signal processing, can voices be transformed more effectively if biomechanical, acoustic, and anatomical scaling principles are applied? The work reported here is an extension of Childer's work (1989) into the physiologic domain.