structural:expansion
Symphonies 4–6 (1935–1948)

The middle three symphonies are purely orchestral, and generally conventional in form, with sonata form (modified in places), specified home keys, and four-movement structure. The orchestral forces required are not large by the standards of the first half of the 20th century, although the Fourth calls for an augmented woodwind section and the Sixth includes a part for tenor saxophone. The Fourth Symphony (1935) astonished listeners with its striking dissonance, far removed from the prevailing quiet tone of the previous symphony. The composer firmly contradicted any notions that the work was programmatical in any respect, and Kennedy calls attempts to give the work "a meretricious programme... a poor compliment to its musical vitality and self-sufficiency".

The Fifth Symphony (1943) was in complete contrast to its predecessor. Vaughan Williams had been working on and off for many years on his operatic version of Bunyan's The Pilgrim's Progress. Fearing—wrongly as it turned out—that the opera would never be completed, Vaughan Williams reworked some of the music already written for it into a new symphony. Despite the internal tensions caused by the deliberate conflict of modality in places, the work is generally serene in character, and was particularly well received for the comfort it gave at a time of all-out war. Neville Cardus later wrote, "The Fifth Symphony contains the most benedictory and consoling music of our time."

With the Sixth Symphony (1948) Vaughan Williams once again confounded expectations. Many had seen the Fifth, composed when he was seventy, as a valedictory work, and the turbulent, troubled Sixth came as a shock. After violent orchestral clashes in the first movement, the obsessive ostinato of the second and the "diabolic" scherzo, the finale perplexed many listeners. Described as "one of the strangest journeys ever undertaken in music", it is marked pianissimo throughout its 10–12-minute duration.