With the concert-installation Bellows, Stefan Maier and Ragnhild May follow in the footsteps not only of Guillaume Dufay, and his motet composed in accordance with the proportions of the Florence cathedral, but also those of Yves Klein and his air architecture, as well as the ephemeral sound spaces of the American composer Maryanne Amacher. On the occasion of the tenth anniversary of their work, they "play" the stones and voids of Saint-Eustache and give them shape them via the sculptural effect of May's instruments, Maier's sound electronics, an ensemble and an organ.