The secret of avoiding monotony with the four-bar module was to vary the accent and the weight of the bars to avoid giving a similar emphatic accent on the first bar of every group, as if one were accenting a downbeat. After Beethoven and before Brahms, perhaps the greatest master of the technique was Chopin, as one can see from the opening of the Nocturne in D flat Major, Op. 27, no. 2, of 1836...

Ch. 4 : Formal Interlude - The Romantic Generation (1995)