This article explores phenomenological open graphic notation as an effective scoring method for instrumentalists engaging with chaotic systems in interactive electroacoustic music. Open graphic notation has long provided composers with a means of fostering interpretative freedom in musical performance. The subjective nature of open graphic scores establishes a dynamic relationship between the score and the performer that parallels the interactions between musicians and chaotic systems in interactive electroacoustic music. Chaotic systems, characterised by their non-linear and unpredictable behaviour, often necessitate improvisatory approaches rather than reliance on fixed notation. However, notation can serve as a structural framework, affording composers greater formal control while supporting performers who may be less accustomed to improvisation. How, then, might notation be used with chaotic systems in interactive electroacoustic music? Drawing on phenomenological concepts such as the lived body, embodied action and Gestalt perception, this notational approach can provide a structured yet flexible means of guiding performer–system interactions. The author presents three recent compositions as case studies, demonstrating how phenomenological open graphic notation can shape and mediate the performer’s engagement with chaotic systems in interactive electroacoustic music.