This article discusses the compositional taxonomy of music theatre works by Constança Capdeville (1937–92) and offers a way to analyse her music and collaborative processes and also the performance of her work through a case study of the piece Double. Capdeville’s works include different elements such as music, settings (staging), movement, text, tape-recorded sound, visual image, props, costumes and lighting. Documentation for the compositions is scattered across different sources or simply lost, making it difficult to reconstruct the works as they have improvised hypothetical components and idiosyncratic or non-standard notations. Using a type of musicological archeology, I want to contribute to the understanding of gesture, language and communication in Capdeville’s works. I aim to preserve the works, particularly by highlighting the collaborative approach of the composer and proposing ways of establishing a documentation process for these aspects in order to systematise the works. I focus on the use of technology of magnetic tape as both a source of listening (the tapes provide a recording of the entire performance) and an instrument (tape recordings are given parts in the composition of the piece). Technology is also an important analytical tool because it helps to track collaborative creative processes. The iAnalyse software is used to help reconstruct and interpret music theatre works.