This paper argues that existing research on the film industry’s conversion to sound largely overlooks the contribution of Lee de Forest and the ‘Phonofilm’ system. Informed by research in De Forest’s personal archive, it suggests that to a certain extent, the development and commercial exploitation of De Forest’s technology contradicts one of the principal implicit assumptions made by historians of this period, that when technology became available which fulfilled certain economic and cultural criteria, its adoption quickly and inevitably followed. Rather, it was De Forest’s refusal to conform to established and increasingly dominant business models that ensured Phonofilm’s failure, even though the technology itself was very similar to that used by the major Hollywood studios in the eventual wholesale conversion.