This paper investigates a few situations where inventive notation has opened the way to new forms of musical expression. After some observations on musical notation from a theoretical perspective, the close relationship between Earle Brown (a New-York School composer) and André Boucourechliev (a French composer of Bulgarian origins) will help define a vivid experimental field in the realm of musical notation. Closely related to the concept of the open work, the unconventional scores of those composers address crucial questions about Western Art music-making in the 1950s. Although less discussed than serialism, spectralism, or extended instrumental techniques, the notational issue encountered by Brown and Boucourechliev is manifested in contemporary composers’ experiments with multimedia/animated scores, and their shift away from textual to digitally augmented notation. This survey of the different solutions adopted by composers will contextualize my own practice-led compositional research, and clarify the notational tools I developed both for the performance of my own compositions, and for pedagogical applications.