I have been listening almost all day to the wonderful works of Alexander Scriaben who was a Russian composer (active years: 1900-1915). He was also a mystic influenced by Theosophy which was enjoying its heyday during that period in Europe. His works have an other-worldly quality about them and he experimented with scales and chords. His works are extraordinary and uplifting. He wrote five symphonies before his untimely death in 1915.
Here is his first symphony which sets the stage for his more daring transcendent later works (The Divine Poem, Prometheus: the Poem of Fire, Poem of Ecstasy, etc). Have a listen.