Of the works of David Tudor, none would seem to be better known than Rainforest IV, his large-scale performed installation of the 1970s. Although it has received widespread and well-documented public performance, Rainforest's germination in the mid-1960s in elements of Bandoneon! (1966) and its evolution over a period of 10 years, from versions I (1968), II (1968-1969), III (1972) and IV (1973) through Forest Speech (1976), have not yet been adequately assessed. This paper follows Rainforest's trajectory chronologically: Matt Rogalsky focuses on the early versions of the work, and John Driscoll describes the collaborative development of Rainforest IV.