The best example I can think of for this sort of style is Gustav Holst's The Planets (1918). Gustav Holst was an English composer of the late Romantic period (some music historians give the 1913 premiere of Igor Stravinsky's ballet Rite of Spring as the end of Romanticism in music, but I don't think the style really died until the 1940's, and The Planets is most definitely a Romantic work). Despite the name, The Planets is really meant to evoke the astrological signs of each of the planets, reducing them to a single emotion, hence my assertion that the piece is rather dualistic in nature. It also tries to evoke an appropriate sense of otherworldliness, which again reflects dualism in that it implies a separation between Earth and the abstract ideals embodied in the other planets. I haven't been able to find a nearby performance of the suite in the last couple of years, and it's not on the LPO's program, but if anybody wants to take a field trip I recommend seeing a performance in person. However, for the sake of convenience here is a YouTube video with a recording of it:
If the style sounds familiar, you're probably hearing John Williams, the composer of the scores for, among other movies, Star Wars, Harry Potter, Indiana Jones, Jaws, and so on. Especially with Star Wars he was inspired by Holst (speaking of which, that famous Jaws theme is a total ripoff of the fourth movement of Antonin Dvořák's Ninth Symphony). Besides that, there are a lot of interesting things happening in the music. For example, notice how the movements sort of balance one another out: Mars ("Bringer of War") is harsh and ominous, Venus ("Bringer of Peace") is light and hopeful, Mercury ("Winged Messenger") is capricious and flighty, Jupiter ("Bringer of Jollity") is majestic, Saturn ("Bringer of Old Age") plods along confusedly, Uranus ("The Magician") is grotesque and disordered, and Neptune ("The Mystic") is ethereal and mysterious. I love the turn in the middle from the relatively conventional and straightforward movements to the otherworldly strangeness of Saturn, Uranus and Neptune. The suite really has to be heard as a single piece for this reason, but my favorite movements are Jupiter and Neptune, for their perfect evocation of joy and mystery, respectively.