Excavated Japanese zithers are likely the oldest surviving stringed instruments in East Asia. This article reviews diachronic changes that occurred in the forms of wood zithers in pre- and protohistoric Japan over approximately two millennia (ca. 1500 b.c.–a.d. 600). It highlights developments such as the addition of resonator boxes, average size increase, and inclusion of figural ornamentation. Results indicate that these formal developments, in addition to the adoption of a seated playing posture as portrayed in Kofun haniwa musician figurines, were driven by the needs of growing communities and their leaders. This analysis suggests that examining changes in musical instruments can be used alongside traditional lines of evidence to research the origins of social complexity and thereby carves out space for a humanistic approach to the study of prehistory.