Thomas Alexandrovich de Hartmann (1885-1956) was a Russian composer and pianist, known for his contributions to classical music and the early 20th-century avant-garde. He was born in the Russian Empire and later became associated with the spiritual teachings of George Gurdjieff, which significantly influenced his musical output. De Hartmann's genre primarily encompassed classical music, with a focus on piano compositions and chamber music. His notable works include "Music for the Piano," a collection of pieces that reflect Gurdjieff's philosophies, and "Hymns and Sacred Songs," which showcases his spiritual and mystical influences. He collaborated closely with Gurdjieff, creating music that accompanied dance and movement, further bridging his compositions with spiritual practices. His impact on music lies in his unique blend of Eastern and Western musical traditions, as well as his role in popularizing Gurdjieff's teachings through music. De Hartmann's works remain of interest for their introspective qualities and their ability to convey a sense of spirituality, making him a significant figure in the context of 20th-century music and mysticism. His legacy continues to influence contemporary musicians interested in the intersection of spirituality and art.