Fold by fold carries the subtitle Portrait de Mallarmé (Portrait of Mallarmé). It is scored for a solo soprano and orchestra and uses sonnets of the French symbolist poet Stéphane Mallarmé. It is Boulez’s longest work (more than one hour) and was composed between 1957 and 1962 with a final version in the 1989, it was first premièred in 1962, conducted by Boulez himself. Boulez explains the use of the soprano through:
The idea of 'setting' a text, however, in the conventional sense, is not adopted here. Rather, the soprano is an integral part of the instrumental fabric and only rarely are specific words or phrases 'illustrated' musically in the traditional manner."
It is a very complex and contrasted work, however its poetical inspiration creates different ambiances and perceptions in each of its movements.