Because Elgar is right for all occasions.
In the years before his first real success as a composer, Elgar relied on choral composition for much of his income.
Unfortunately, these time-consuming, large-scale works were not always the most efficient of payers. Luckily for Elgar, he had been befriended by a senior figure at the music publishers Novello. August Jaeger was someone who genuinely appreciated his music and he was immortalised as ‘Nimrod’ in Elgar’s Enigma Variations.
Having had a pretty unsuccessful sortie into London to make his musical fortune in the 1880s, Elgar retreated to Malvern, from where he wrote, bemoaning his fate to the ever receptive Jaeger. Complaining of lean times, he sent Jaeger a violin piece called Evensong, suggesting the name could be changed to Vespers if needed. In the end, the publisher preferred to call the piece Chanson de Nuit.
A couple of years later, Elgar wrote to Jaeger again, claiming to have recently rediscovered its companion piece. The two works provide a simple day-and-night contrast of styles, with Chanson de Nuit being very much the richer of the two. Chanson de Matin, as its name would suggest, is simpler and fresher.