In the Netherlands, new music was in a process of development and professionalization from ca. 1900 onwards; after WW II the interrupted thread was picked-up again, to be suppressed again with the intervention of younger composers in the sixties who wanted to follow international modernist ideologies rather than further develop the musical tradition. Dozens of active composers were condemned for being oldfashioned, bourgeois, 'behind the times', or worse, representing an ideologically-burdened past, like the excellent tonal composer Henk Badings who opportunistically took his chances with the German regime to boost his career which resulted in total censorship of his music after the liberation.... this despiccable collaboration threw a shadow over all of his collegues who had preserved their human dignity and had either emigrated or stopped writing and performing.
To show the impressive level of serious composition in those premodernist times, here is a specimen of symphonic music by Marius Flothuis, who survived concentration camps and after the war was artistic leader of the Concertgebouw Orchestra. He was also an internationally-renown musicologist who presided over the Zentralinstitut für Mozartforschung in Salzburg.
This is his 'Symphonic Music' from 1957:
Flothuis is hardly played nowadays, only his chamber music occasionally finds a hearing. But if there had not been war, serious music in the Netherlands could have developed in an internationally-appreciated and performed body of music, comparable with music from England, Poland, Spain, or Italy. The 'new music establishment' in Holland, centered around the national and monopolizing Fund for the Performing Arts which 'controls artistic quality' (its openly formulated mission), now prefers hip, conventional modernism mixed with Americanism, and nonsense, to the detriment of older existing music like Flothuis', or Hans Kox, who stubbornly worked on the fundament of serious music.
Some samples of representative Dutch 'new music':