Although the xylophone easily conveys “happy” and/or “light-hearted” affects, it is rarely chosen by composers to convey sadness. Does this typecasting merely a lack of imagination, or a fundamental constraint of the instrument’s design? This question connects with a growing body of research exploring the relationship between instruments’ structures and their musical uses. It also holds important consequences for percussionists interested our repertoire’s evolution, and those interested in future directions (i.e., commissions, interpretation of new works, improvisation). Using demonstrations of standard repertoire, my presentation will synthesize insights from music cognition, linguistics, and acoustics, along with performance demonstrations offering an interdisciplinary perspective on how repertoire for the xylophone has evolved to its current state. This will help clarify how the xylophone’s acoustic constraints and affordances shape its emotional repertoire, offering insight useful for composers and performers of percussion literature alike.