Music evolves with the times. Unknown instruments appear regularly and, without giving up those cherished by Mozart and Beethoven, young artists are interested in these new possibilities of expression. This is the whole principle of «mixed music»: combining classical acoustic instruments and technologies born from the progress of electronics. As part of its initiative «En scène!» , which each year allows several hundred students of conservatories to perform in front of an audience, the department of Val d'Oise has pushed young musicians to move in this direction. They first attended a concert of the Festival de Royaumont 2023 given by Semblance. The ensemble notably performed a piece by the American Catherine Lamb designed for seven oscillators in the heart of the Magic Square, a space where loudspeakers hide among the plants. Then the students of the seven music schools involved in this project benefited throughout the year from workshops given by their elders. They gradually tamed the computer tools, as well as a different system of graphic notation. A new electro-acoustic piece has matured in each establishment. For this new edition of «En scène!» , all the young musicians meet again in the Magic Square but, this time, it is they who will be applauded, for their own creation. The collective finale will gather all the musicians around a monumental work by the British composer Cornelius Cardew (1936 – 1981), Treatise, a 193-page set with only graphic indications. It is the turn of a new generation to reinvent the work, to imagine its own rules and to rethink the abstract link that links interpretation to the score…