Arnold Schoenberg is a renowned Austrian composer who is famous for pioneering the atonal music movement. He is also recognized for his contribution to the development of the 12-tone technique, which allows composers to use all 12 notes in an octave without giving preference to a particular note. Some synonyms that can be used to refer to Arnold Schoenberg include avant-garde composer, musical innovator, and radical musician. He was an influential figure in the development of modern music and his works, which were often controversial, had a significant impact on the music industry, paving the way for new and exciting musical trends.