"I frequently compose out the entire metric structure of a piece in modified cyclic form, where each cyclic revolution undergoes some form of 'variation' much as if measure lengths were concrete musical 'material.'"

Brian Ferneyhough, a composer frequently associated with the "New Complexity" motion, discusses an elaborate method to musical structure in this quote. Here, Ferneyhough exposes his method of structuring a piece utilizing an idea called "modified cyclic type". In music, cyclic type is a method where a theme, motif, or other structural component repeats throughout a piece, offering unity and cohesion. This type is often found in large-scale structures where ideas are reviewed and changed across movements.

Ferneyhough, however, speaks of a "modified" variation of this form, suggesting that while the music returns to particular cyclic elements, these aspects aren't merely duplicated; instead, they go through a procedure of "variation". This suggests a level of imagination and transformation, where each recurrence of a cycle brings something novel or altered to the table. It's as if the cycles are dynamic, breathing entities within the composition.

The phrase "measure lengths were concrete musical 'product'" signifies how Ferneyhough deals with time and rhythm almost as tangibly as melodic or harmonic material. Traditional structures typically focus on pitch and consistency, however Ferneyhough places equal, if not more, emphasis on the real "architecture" of the music-- the metric and temporal structures. By developing step lengths as material, he crafts a composition where time signature changes and rhythmic complexity are as crucial as melodic development.

This careful structuring procedure results in compositions identified by intricate rhythms and a dense, textured sound world, needing both performers and listeners to engage deeply with the music's temporal landscape. In essence, Ferneyhough's quote shows how he sees musical time and rhythm as foundational aspects of structure, deserving as much exploration and advancement as melody or harmony. His approach engenders an unique listening experience, one in which traditional understandings of musical time are expanded and enriched.