This paper examines Summermood (1981), an electroacoustic work composed by Antonio Russek for bass flute and live electronics, situating it within the Mexican electroacoustic scene of the 1980s and in dialogue with international developments in live electronic performance. A pivotal work in both Russek’s career and flutist Marielena Arizpe’s repertoire, Summermood, stands among the earliest Mexican compositions for electronically modified acoustic instruments. It has not been able to be studied or performed due to the absence of published documentation, its dependence on the obsolete DeltaLab DL-4 digital delay unit, and its original association with Arizpe, who retired early following an accident-related injury. Drawing on archival documents, interviews, recordings and the graphic score and Russek’s notes, this paper analyses the work’s aesthetic conception, its integration of extended flute timbres with electronic processing, its graphic notation and the collaborative practices that informed its creation, arguing for its significance in the historiography of Mexican electroacoustic music. While briefly acknowledging the preservation challenges posed by obsolete technologies, the central aim of this paper is to reassemble Summermood as a case study that illuminates Mexico’s underexplored contribution to the global avant-garde of the late twentieth century.