My dissertation elucidates how art practice can be a useful and helpful model for learning, teaching, and conducting research for HCI and the broader STEM fields. It focuses on "improvisation", a fundamental strategy and skill often used in the broader genres of arts, including cool jazz and the avant-garde. To achieve this goal, this dissertation provides three main chapters in which individual chapters explore different but interconnected topics about improvisation and aesthetic engagement for HCI. The first chapter, "Intermodulation", embarks on theory building about improvisation. Based on various studies of improvisation drawn from art, music, HCI, the social sciences, and two ethnographic studies, we identify five key features of improvisational action ("reflexivity, transgression, tension, listening," and "interdependence"). With this theoretical foundation, the second chapter, "Tech-Art-Theory", explores the implementation of improvisational practice in HCI and STEM education. Based on three pedagogical interventions of our own at Cornell University, we point out three specific pedagogical conditions ("socio-material evaluations, multi-sensory practices," and "making safe spaces for error") that can support improvisational ways of learning and computing. In the third chapter, "The Electronicists", we finally build our own research/inquiry framework called "techno-aesthetic practice" that pursues mediated creativity from the situated negotiation of engineering, art, and humanistic inquiries, including through the production of "techno-aesthetic objects" that can travel across and in some measure connect these worlds. The fourth chapter also provides an "Online Gallery" in which readers can find various curated audiovisual data and artworks that our research team has collected and produced during our ethnographic studies in the above chapters. Finally, this dissertation answers the question "How can HCI and STEM practitioners living in the early 21st century to benefit from improvisational art practice as a model of learning, teaching, and research?" [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]