Sibelius's Fifth Symphony is perfect. Every single note in every single chord leads perfectly into the next note, the next chord, the next phrase, the next section, the next movement. Even the smallest, most impressionistically hazy notes matter.
Perfection is not the greatest of all virtues. There are plenty of other composers for large orchestra, towering ones like Handel, Berlioz, Mahler, Strauss, Elgar, Shostakovich, Messiaen, who extravagantly throw their notes around by the fistful. They are masters of inclusion - everything they can think of goes in. All of them lived the vast majority of their lives in great, ethnically diverse metropolitan centers. One might almost hear a reflection of the extraneous noise and people with whom they'll never come into contact in their music.
Sibelius, on the other hand, was one of the great excluders - like Bach, Brahms, Mendelssohn, Bartok, Debussy, and arguably Bruckner. All of them certainly spent their time in great metropoles, but usually not the biggest or most diverse. The genius of this latter group comes from leaving out everything extraneous from the essence of the work. Every note has a formal relationship to every other note: at their considerable best, their music is put together with the veracity of a mathematical proof.
When Sibelius began, he was a big splashy Romantic - taking at liberty from Wagner, and Tchaikovsky, and Bruckner, and even his contemporary Richard Strauss. But starting in 1904, Sibelius became an entirely different, perhaps far deeper, composer. 1904 was the year that Sibelius moved into his estate: Ainola, purchased for him by the Finnish government. Before 1904, Sibelius was a 19th century romantic. After 1904, he was a 20th-century neoclassicist.
But Sibelius's neo-classicism has little if anything to do with the Francofied neo-classicism of Poulenc and Stravinsky. Sibelius writes the beautiful nature he sees on his estate. He strips the most Teutonic of all forms: Sonata/Allegro, down to its essence. The form of the Fifth Symphony is all too simple: A opening movement that starts slow and gets faster, then a charming interlude, then a finale that starts fast and gets slower.
How does he do it? With the effects of nature. All throughout, you hear the sounds of stillness, wind, rain, thunder, lightening, animals, and sunshine. Sibelius's effects of nature are unmistakably vivid and onomatopoetic. It begins with a still sunshine, and describes a storm stretching over the horizon. The second movement sounds unmistakably like the beauty of a wet landscape right after the storm - you hear plucking strings all throughout like rainwater dripping from tree leaves. The final movement begins with more rain, and ends with what can only be described as a blaze of sunshine.
Two things about the finale should remain with the listener forever. One is 'The Swan Hymn.' A repeated three-note horn call that's understated but unmistakable - I'll allow Sibelius to describe his experience of sixteen swans flying in formation over him:
"One of my greatest experiences! Lord God, that beauty! They circled over me for a long time. Disappeared into the solar haze like a gleaming, silver ribbon... That this should have happened to me, who have so long been the outsider... The swans are always in my thoughts and give splendor to [my] life. [It's] strange to learn that nothing in the whole world affects me - nothing in art, literature, or music - in the same way as do these swans and cranes and wild geese. Their voices and being"
The other is the final measures, with long pauses in between - like great shouts of joy to a landscape which you hope hears you.
There are three great performances of Sibelius 5 of which I know. This, by Eugene Ormandy and the Philadelphia Orchestra, may still be the greatest, more than sixty years after it was set down.