Psychological research investigating sound and music has increasingly been adapted to the evaluation of soundtracking for games, and is now being considered in the development and design stages of some titles. This chapter summarizes the main findings of this body of knowledge. It also describes the application of emotional measurement techniques and player responses using biophysiological metering and analysis. The distinction between different types of psychophysiological responses to sound and music are explored, with the advantages and limitations of such techniques considered. The distinction between musically induced and perceived emotional response is of particular relevance to future game design, and the use of biophysiological metering presents a unique opportunity to create fast, continuous control signals for gaming and game sound to maximize player experiences. The world of game soundtracking also presents a unique opportunity to explore sound and music evaluation in ways which traditional musicology might not offer (for example, deliberately antagonistic music, non-linear sound design and so on). The chapter concludes with directions for future research based on the paradigm of biofeedback and bio-controlled game audio.