The Greek word εντασις​ means “tension,” “straining,” “exertion.” It was used in architecture to indicate the swelling in the outline of a column, and in music to describe the tension of the strings in a lyra. The verb εντείνω, that has the same root, refers to any operation performed with straps or cords. Broader meanings include “intensify,” “carry on vigorously,” “exert oneself,” “be vehement.” The adjective εντατικός adds to these meanings the idea of something “stimulating,” “aphrodisiac,” “sexually vigorous.” The “entasis” counterbalances the perceived narrowing of the column and provides visual harmony. The Greeks used it to express strength, and emphasize the effort of the columns that support the weight of the trabeation. The swelling that characterizes the middle part of the columns symbolically expresses the pressure exerted by the trabeation.
Entasis has been conceived as a multi-layered composition, where elements apparently incompatible, and different languages are forced to work together in constant  friction. They evolve and change, passing through different states of matter, from rigid to fluid shapes. In planning this piece, what I had in mind was a dynamic system of forces, where masses of sound either undergo processes of erosion and crumbling, or are frozen in rigid structures; I thought of areas featuring chaos and molecular agitation, or slipping platforms that betray the expectations of the audience. The use of sandpaper blocks and chains in crucial points of the score seems to summarize these concepts. The sand is the result of disintegration and crumbling of rock, and also represents the flowing of time in the evocative object of the hourglass. Chains, on the contrary, are a symbol of captivity and constriction of movement. Nevertheless, they have a timbral connection, like all the elements apparently unrelated of Entasis, which features rigorous procedures in the generation of all the materials used.
The series used in Entasis undergoes several processes of transformation, that create sub-materials, such as the Constellations, generated by the concentric rings of the matrix, or further rows generated by rotational arrays.

When the constellations appear for the first time in the score, at m. 70, they are highly recognizable. They stand out in the high register of piccolo and flutes and every note has a duration of nine quarter notes. They are bright, yet distant and incomprehensible, like stars, and move at their own pace, heedless of what is happening on earth to human beings. The constellation materials are mainly used in two ways. They either move very slowly and follow a regular rhythmic pattern - as in their first appearance - or very fast, and articulated in irregular groupings, as we can observe in the section from m. 140 to m. 170. They are also used at the end of the work, in the “Cadenza finale a due,” as a conclusive and intimate clausola. The piece ends re-winding in itself, in its spiral of concentric rings, after a difficult journey.
In Entasis the performers are required, in some passages, to whisper or loudly pronounce some Latin words from the section of Vitruvius’ treatise De architectura  (mid-20 B.C.), where he explains the concept of  “entasis.” They comment on the action, like the Greek choir did in ancient tragedies, and are meant to represent the internal reaction of the audience to the most mysterious passages of this score. Among the materials and the techniques adopted in Entasis, there are some elements belonging to the past, like the choral, the canon and the clausola. From m. 155 to m. 185, the string section is built as a long canon, based on irregular augmentations and diminutions of the RI series. This reference to ancient techniques is common in contemporary Western tradition, especially if we think of the way in which Ligeti used ancient polyphony or the interpretations of the orthodox chants Penderecki offered in his sacred compositions.
Mm. 221-239 show the maximum level of compression of the chord structures, to enhance the feeling of liberation created by the partially aleatoric section (mm. 240-268) that leads the piece to its conclusion. The process of saturation of the materials is here fully unfolded. The fermata of m.268 marks a moment of apnea in the performance, and the gradual distension of the passage in mm. 269-280 is the consequential exhalation after this breath-held moment. The sound gradually disappears in the diminuendo from pp to niente. The “Cadenza finale a due” brings the piece back to the initial chord. The intervention of the chains closes the piece, and the audience is merged in the silence of the concert hall. Entasis disappears like a dream.