Composed and realized during the spring of 1961 to accompany the projections of the spectacle ‘Forms and Light’ conceived by Nicolas Schoeffer for the Congress Palace of Liège, this work was immediately removed by the municipal authorities of the town and replaced by some ‘milder’ music. It must be said that in view of what seemed to me a too decorative aspect of the visual pat of the spectacle, I took care of respecting consciously the precise chronometric program which was imposed on me. Moved by observations about the ‘realist’ possibilities of the electro acoustic material which I had made during previous years, I intended to realize highly ‘evocative’ musical scenes: not only for what concerns the physical nature of the sound but also in relation to history, even the most recent one (big strikes at the end of 1960) from the surrounding region. In this way it was not difficult to assign three rather precise titles to the different parts: ‘Air and water’, ‘Voices of the town’ and ‘Smelting-Works’, and to send into this world this musical and socio-graphical triptych for an autonomous existence: it defended itself rather well. The record, made in the USA, has had a solid success. The piece has still been realized with the help of the primitive and rather boring techniques of ‘micro-montage’ which obliges us to be very conscious of every single element. The composition somehow anticipates (like Stockhausen’s Kontakte) more global production-methods which became possible somewhat later by the introduction of analogue synthesizers and later by digital techniques. The piece integrates (like my Électre or Stockhausen’s Gesang der Jünglinge) in an intimate way ‘concrete’ material (for example the voices, denaturised until the point of total abstraction) and purely ‘electronic’ (synthetic) elements. Thus I tried to give a musical portrait of the city of my youth.