This chapter explores the concept of agency in digital gameful compositions (DGCs), emphasising how musical meaning emerges through performer interaction with game mechanics. Drawing on semiotic frameworks, the chapter distinguishes between the composer’s intent (poiesis), the performer’s interpretation (esthesis), and the game system as a neutral artefact. We introduce the ideas of possibility space, decision space, and the hierarchy of interactive forms (toys, puzzles, contests, games) to analyse how performers navigate and shape musical outcomes. The chapter also examines how uncertainty, competition, and accessibility influence player experience, referencing psychological models of motivation and flow. Finally, it addresses audience experience, including ideas of score transparency and participatory design, highlighting the dual role of performers as both players and musicians.