Birtwistle's source of inspiration here was twofold: firstly, an admiration for the music of Isaac, the 15th century Flemish master, whose instrumental canzonas he had been writing out for his pupils at Cranbourne Chase to play; and secondly, a visit to the Picasso exhibition at the Tate Gallery. At the Tate, some prominence was given to a number of studies in which Picasso had taken various aspects (technical and material) of a picture by Velasquez and had expanded and exploited each in a painting of his own. Birtwistle decided to take a group of Isaac canzonas and treat them in the same way. This does not mean that listeners will necessarily trace resemblances in the way that a Vittoria motet is recognisable in its kindred mass; they are there to help the composer rather than the audience.
The work is divided into alternate verse and chorus sections. The verses, for instance, are all wind solos with guitar, successively flute, clarinet and oboe, whereas the choruses use larger groups and are joined by the guitar only in the finale. There is a reference in the last chorus to Isaac's canzona Der Welte Fundt, from which the work derives its title.