Commissioned by the Teatro dell'Opera in Rome, and premiered there in 1968, 'Work in Progress' is an artistic experiment drawn from ideas and concepts explored throughout Calder's decades-long career. It is a world of his own design. His "ballet without dancers" is full of moments simultaneously nuanced and unpredictable, including set pieces that psychedelically visualise the natural world, dynamic arabesques drawn by cyclists on stage, and a glorious finale of mobile structures in motion. After watching the dress rehearsal in 1968, Calder told his friend Giovanni Carandente, "I should have called it my life in nineteen minutes".