This chapter explores the phenomenon of play in the context of professional chamber ensemble rehearsal and argues that play lies at the heart of it. The account begins with an interrogation of the concept of play and a distinction is made between “playing music” (that is, how the term play is ordinarily used in making music) and “play” (that is, the social and cultural activity that manifests in many contexts). Characteristics of play are identified according to existing research conceptualisations (e.g. Huizinga [1938] 2016; Karoff 2013; Eberle 2014; Henricks 2018). Within the domain of musicology, it is noted that previous studies on play and music performance focus on activity about scores and sounds (e.g. Stubley 1993; Reichling 1997; C...