For 10 points, name this Russian Symbolist composer of the unfinished Mysterium and Prometheus:
This composer's ninth piano sonata opens with a chromatically descending melody in 4/8 harmonized in alternating major thirds and diminished seventh intervals. His third symphony has movements titled "Luttes", "Voluptés", and "Jeu divin". This composer invented a synthetic chord that stacks two perfect fourths on top of an augmented fourth, a diminished fourth, and another augmented fourth. One work by this composer of the "Black Mass" Sonata manipulates his "mystic chord" and requires a "color organ" to project synesthetic effects. An unfinished symphonic work by this composer of The Divine Poem was meant for a performance in the foothills of the Himalayas followed by the end of the world. For 10 points, name this Russian Symbolist composer of the unfinished Mysterium and Prometheus: The Poem of Fire.
This composer's ninth piano sonata opens with a chromatically descending melody in 4/8 harmonized in alternating major thirds and diminished seventh intervals.
Alexander Nikolayevich Scriabin