Play-in particular adult-child play – is an important component of child development. This article investigates how to design for adult-child play through Sound Happening, an interactive installation for musical play. We present a preliminary analysis of participant interactions with Sound Happening at The Children’s Museum of Pittsburgh, where a total of 112 children and 53 adults interacted with the exhibit. The data from these interactions indicates that Sound Happening can facilitate both verbal parental engagement and partnered adult-child play. We highlight several features of Sound Happening that can be used as design principles for adult-child play environments. These include incorporating embodied interfaces, designing for multiple levels of engagement, and utilizing culturally recognizable interaction modalities. © 2018 Association for Computing Machinery.