Le Grand Marcel is an amateur orchestra that meets in Montreuil at least twice a month throughout the year. Open to all, it is a collective musical practice meeting led by the double bass player and composer Théo Girard.

At the beginning of the project in 2018, the work was based on compositions by Théo Girard adapted from his large orchestra Pensées Rotatives, but to renew the repertoire, everyone is now warmly invited to bring an idea or a composition in order to open the orchestra to multiple sounds. From the work of the repertoire (on score or by ear) and from improvisation sessions, the fundamental notions of music are approached: listening, reading, rhythm, tempo, improvisation, sound, silence, nuances, technique, concentration. The circular configuration of the rehearsals requires a great deal of concentration and also allows each person to be in the best position to listen, share and be aware of the group. As it is composed largely of people who do not have the opportunity to play in a group, it is essential to feel the unity of the group.