Things don’t always go to plan. You go on holiday, hoping to be inspired to great things, but it rains and rains. You sit down to write a little piece for chorus and orchestra and you run out of ideas. At least two composers on the BBC National Orchestra of Wales’ programme with conductor Martyn Brabbins hit the buffers before changing direction and producing something magnificent. All three pieces were born out of a certain degree of frustration; all three composers must have known the feeling of looking out of the window and praying for inspiration.

Elgar made the most of a disappointing trip to Italy in 1904, sketching out at lightning speed the material for a concert overture once the sun came out. The result is a big-boned overture that’s almost a symphony; indeed, In the South (Alassio) sprang from aborted plans to write a symphony for an Elgar Festival to be held at Covent Garden. Its sweeping opulence reminds us that Elgar was, along with Richard Strauss, one of the great musical landscape painters of his age. This impression was enhanced by Brabbins’ well-judged combination of momentum and stately grandeur and by the voluminous tone of the orchestra’s strings, whose subtle inflections of phrasing rode the wave of Elgar’s glorious orchestration.

At its centre, a little moment of tender naivety tied In the South to its neighbour in the concert’s first half: something of a rarity, Frederick Delius’ Double Concerto for violin and cello. The composer, hard-up and fearful of the First World War enveloping the land around his French home, had apparently been inspired by Brahms’ Concerto for the same pairing, despite his general antipathy towards the German composer’s music. His disparagement of the music of others wasn’t unusual, but his own music tends to inspire real devotion among his fans, who include violinist Tasmin Little. Little has herself made a speciality of Delius, and though I’ve not always been convinced by her advocacy in the past, I was here. At its best this music has the hour-after-sunset glow that characterises much of his work. Though in one movement, three fairly conventional sections hide within, with the fragile beauty in the heart of the work most affecting of all. Delius’ meandering, motivic writing ties the violin and cello together, not in competition but in partnership. From my seat, Paul Watkins’ hugely active cello part vanished somewhere into the hall’s acoustic, but what remained clear was the impression of sensitive dialogue between the two soloists.

If the first half had been about composers inspired by their surroundings – Elgar’s Italian holiday and Delius’s perennial love affair with his quiet retreat in northern France – the second looked back to the biblical days of Babylon. William Walton’s brief had been to compose a small choral work; it grew and grew by 1931 into Belshazzar's Feast, a piece about which nothing is small. Walton had nearly given up in the middle, but pressed on as the piece changed out of all recognition. Thomas Beecham, such a supporter of Delius, had quipped to the younger Walton: “as you’ll never hear the thing again, my boy, why not throw in a couple of brass bands?” Brass players have appreciated the extra work ever since.

Walton’s music trades in a kind of jaunty rhythmic thrust totally alien to Delius’; handily, Brabbins had the BBCNOW, the BBC National Chorus or Wales and members of Bristol Choral Society superbly drilled, ready for all of Belshazzar’s eruptions of anguish and joy. The Jews of Babylon pledge revenge for the sacrilege committed by King Belshazzar, whose praise of pagan gods here produced climaxes of tremendous power and consistency. Indeed, everything about this impressive performance was secure; I only hankered after a little more drive from Brabbins and a greater sense of pitch in bass Neal Davies’s forthright delivery. The chorus, though, demands “make a joyful noise”, and they certainly did that.