Following early variants in the classical avant-gardes, the first art projects inviting spectators to interact with audiovisual systems date back to the 1950s and 1960s. Participatory assemblages, performance art, action art, kinetic art, and cybernetic art all called the traditionally object-oriented conception of the artwork into question, favoring a more process- and event-oriented understanding. This led to a greater degree of stimulated activity on the part of the recipient of the work, as well as the incorporation of mechanical elements and electronic media. The first systems offering possibilities for technically supported interaction were based almost exclusively on acoustic input that generated movement, light, and/or sound as output. In the 1960s and 1970s, the spread of video technology, on the one hand, created possibilities for real-time playback and manipulation of motion images; on the other, the advances made in computer technology enabled real-time interaction between humans and computers as well as the first graphical images. This paved the way for digital systems with elaborately programmed feedback processes, such as those developed by Myron Krueger and David Rokeby in the 1970s and 1980s. While these artists still focused on the manipulation of either visual or acoustic information, since the 1990s interactive art projects have been created that involve the joint manipulation of acoustic and visual information by the users. Artists such as Toshio Iwai, and Golan Levin and Zachary Lieberman have since developed a range of interactive art projects based on mainly abstract, at times also associative relations between sounds, colors, and forms, which are activated, manipulated, or indeed newly created during the interactive process.