"Developing ALPS — Notes on Agency in Technology" collects the written outcomes of my applied doctorate in music (scientific strand). This thesis is a report and a reflection on the development of tracking technology for use in interactive sonic arts. It outlines its background, methods and outcomes, a collection of articles marking milestones within the project, and a reflection on agency in technologies – digital ones in particular. Taking my own (music-)technological practice as a starting point, I scrutinise the notion of agency in human-machine interactions and relations, both in the post-humanist conception and with respect to the Gaia principle.