The underlying structure of Ajar develops out of the repetition of four eight-note chords, a kind of passacalia or harmonic continuum, which functions as an invisible foundation for various processes of transformation of the material. The chords, which emerge from the selection of individual, isolated notes, are progressively expanded until their homony is completely filled out; they are then subjected to processes of compression, expansion, polarisation and transposition in an increasingly intense rhythmic progression.

As a result, the writing – which begins as "horizontal", heterophonic and fragmentary – becomes progressively oriented, through various combinations of instrumental timbres, towards a pronounced verticality.

In the final passage, small gestures converge in an atmosphere of increasing sonic rarefaction. This leads to a thinning out of the harmony, which continues until the final chord, reduced to its simplest elements, ultimately folds in upon itslef around its lowest note.