The author composed this work in 1957 and 1958 before his arrival at the Groupe de Recherches Musicales of the R.T.F. (French Radio and Television). It represents an attempt at conquest of a certain number of degrees of an imaginary and already concrete range.

The first degree is the exploration of an interval located in the low register of the instruments.

The second degree is that of the unforeseeable events (accidents) causing a disturbance in the continuity.

The third degree is that of the superimposed rhythms, or the irregular iterations.

In the fourth degree, the dynamic profiles (variations of intensity) are superimposed producing slowly evolving sound screens.

The fifth degree represents a play of musical objects; transpositions of visual objects (various rhombuses, spirals, crosses and angles).

The sixth degree is that of the play with heights, dispersion and bringing together notes with variations of duration.

The seventh degree is a fast dance going slowly to high instruments (progressive disappearance of the low instruments).

The eighth degree completes the work by melodic structures that evolve near the high frequencies.

Prize of the Biennial of Paris in 1961