Cod.Act’s Pendulum Choir explores the relationship between gravity, vocal movement in space and choral composition by placing a 9-piece choir on tilting, continuously moving platforms. A revolving, undulating hydraulic jack supports each singer. These movements have a direct physical impact on the singers, causing specific sonorous effects. The performance is constrained not only by the effects of gravity on the body and lungs but also the interaction in space between singers as they move in and out of close proximity with one and another. In this sense Pendulum Choir can be viewed as a system of local entities interacting to create global behaviour – individual voices merge to create complex polyphonies guided by spatio-temporal movement and gravitational force. Although there is vocal autonomy for each singer, the overall impression is one of a single controlling robotic intelligence – a many-headed cyborg hydra. Visually we are reminded of multiform systems such as those found in magnetism or particles affected by elastic forces. After initial explorations into the relationships between movement and sound using the hydraulic platform system Cod.Act realised that the effects these spatial and gravitation constrains had on the vocal abilities of the singers could be harnessed as a compositional parameter in itself. This is a prime example of how an explorative technique can generate new parameters to be exploited in the compositional process. Gravity and spatial configurations not only affect performance but have also driven the composition from the outset. The composer and architect saw evocations of a living organ, a lung and subsequently realised the composition’s narrative, sonically and metaphorically, according to the workings of the respiratory system. Each singer represents one of the lung’s alveoli. The authors suggest that the music is based on readings of Virgil, Ovid and Horace: “The choir blows and sings the breath. It travels from life to death, exhales, suffocates, loses its equilibrium while recounting its sensation of the last breath on its descent to hell”. The voices appear to be generating the movement of the machine and being affected by it simultaneously – suggestive of a feedback loop. This two-way process is reflected by cycles of sonority that recall previous cycles and further create an accretion of vocal motifs. The echoes of the breath instantiate a kind of robotic Pranayama where the machine derives its life-force from the choir. Cod.Act is André and Michel Décosterd, respectively a musician/composer and an architect, a team that develops artistic productions, performances and interactive installations using devices to translate physical movement into sound phenomena.