Beethoven set the standard for boffo , exuberant, and loud symphonic endings, After him most composers followed his example most of the time. But not always. I picked four examples of great symphonies that end softly. I’ll take them in chronological order.
Brahms’ third symphony written in 1883 has a lot of vigorous music in its last movement. Near the work’s conclusion it quotes a theme heard in the first movement and then ends softly. There is nothing drawn out about this quite ending; its seems a natural conclusion to what has gone before it. Brahms Symphony #3 finale.
Tchaikovsky’s sixth and last symphony (1893) has been called a suicide note. I don’t know about that, but the whole last movement seems about death. The symphony just dies away. The highly energetic third movement is followed by a beautiful adagio with this ending: Tchaikovsky Symp #6 finale.
Mahler’s last completed symphony (1910), his ninth, outdoes anything that had preceded it when it comes to softness. It’s ending is so quiet that it’s hard to tell when exactly it’s over. When properly performed it is an exceptional and deeply emotional experience. It’s another symphony about death. Mahler Symphony #9 finale
Shostakovich’s fourth symphony is the most unusual he ever wrote. It was completed in 1936, but not performed until 1961. The composer had gotten into serious trouble with Stalin who considered himself a great music critic. Had Shostakovich gone ahead with the premiere of the 4th symphony it literally might have caused his death. The work is in three movements, is the most dissonant he ever wrote, and is a gigantic and magnificent meander. It needs about 100 musicians; it’s outer movements are each about 25 minutes long; the middle lasts about 9 minutes. The final movement seems to be building to a shattering conclusion when it descends into about six minutes of quiet. This is the Shostakovich symphony most influenced by Mahler. When you listen to its end you’ll easily hear why. Shostakovich Symp #4 finale.