The selection of repertoire is a critical component of ensemble music, especially in educational contexts. Accredited music education systems often rely on required, recommended, or prescribed music lists to assist in these selections. Nonetheless, previous content analyses have primarily focused on questions of creative quality, artistic merit, and educational appropriateness while overlooking crucial demographic factors such as gender identity, ethnicity, race, and vital status of included composers. I examined gender and ethnic diversity within wind band repertoire lists from 10 states representing five geographical regions. The lists contained 17,281 total works by 1,221 identifiable composers, predominately White (92.63%) and male (95.58%). K-means clustering revealed two unequal composer groups, with the smaller, predominantly White and male subgroup accounting for 40.82% of works and a high per capita representation across lists. Principal components analysis showed composer ethnicity, gender, and vital status interrelated across data dimensions. Despite latent list differences, composer diversity across and within lists was extremely limited. If ensemble directors are to meaningfully engage in diversifying the repertoire their students perform, expanding beyond the existing collection of predominantly White and male composers is a necessity.