An early photo shows little Arnold in Vienna holding the hand of his Jewish mother. The five-year-old's gaze was already filled with curiosity and energy.

When he died in Los Angeles in 1951 at the age of 77, he left behind a far-reaching legacy — musically, artistically and politically.

"Arnold Schönberg was not only a composer and painter, he was also incredibly important as a teacher, an educator, a writer, a theoretician and an inventor," says Ulrike Anton, director of the Arnold Schönberg Center in Vienna. "He inspired an entire century with his belief in progress."

There is always a future for anyone who is ready to cross boundaries — that was one of his guiding beliefs.

This is demonstrated by the stages of his life and many of his groundbreaking moves: from his musical beginnings in Vienna or his autodidactic composition studies with Alexander Zemlinsky in Prague, from his life as a composer and music professor in Berlin and Vienna, to his move to the US when the Nazis seized power in Germany in 1933.

Music runs like a thread through Schönberg's life. He attended open-air concerts in the Vienna Prater throughout his youth and started learning the violin at the age of nine. By 1899, just 16 years later, he had already composed his first major work, "Verklärte Nacht," (Transfigured Night) a string sextet.

It was followed by works including "Friede auf Erden" (Peace on Earth) op. 13; the Chamber Symphony op. 9; his String Quartets No. 1 op. 7 and No. 2 op. 10; "Erwartung" (Expectation) op. 17 — and above all the famous "Gurre-Lieder" (Songs of Gurre).

"Musically, he comes from the late Romantic period," says Schönberg expert Ulrike Anton. His great role models were Johannes Brahms (1833-1897) and Gustav Mahler (1860-1911). But Schönberg also found inspiration in the works of Ludwig van Beethoven (1770-1827) and Johann Sebastian Bach (1685-1750). "He processed traces of the past — and then took them to completely new shores," adds Anton.

And while he was working on his music, Schönberg was also painting, starting around 1907. On paper or on canvas, he created expressive portraits and self-portraits or delicately colored explorations of nature, as well as modern interpretations of religious themes, such as the yellow "Christus-Vision" (Vision of Christ) from 1919.

Wassily Kandinsky and his circle of artists, known collectively as The Blue Rider, had included Schönberg's paintings in their exhibitions in Munich. Schönberg ultimately painted around 70 works.

Breaking with musical tonality

But Arnold Schönberg is perhaps most famous for breaking new ground musically.

From 1908 onwards, he started challenging the traditional boundaries of tonality, which has been the dominating principle in most Western music since the 17th century and which continues to guide the compositional principles of music we are used to hearing today.

His String Quartet No. 2 (1907/1908) is considered an early milestone of atonal music.

The artist fell into a creative crisis, from which he developed a completely new method of composing by 1920/21 — the "12-tone technique," by which all white and black piano keys within an octave — 12 tones —  are used, going way beyond the notes belonging to the traditional major or minor scales.

Schönberg's technique dictated that any note could only be repeated after all 12 chromatic notes were played once.

With this system, Schönberg gave his works a theoretical foundation.

"The development of this method makes Schönberg one of the great innovators in history," says Ulrike Anton, adding that it is "comparable to the Art Nouveau architect Otto Wagner (1841-1918), the philosopher Ludwig Wittgenstein (1899-1951), the psychoanalyst Sigmund Freud (1856-1939) or the physicist Albert Einstein (1879-1955)."

The protagonists of Viennese modernism all had one thing in common: They shared the spirit of optimism that characterized the beginning of the 20th century.

Emigration to the USA

After the death of his first wife in 1923, he married for a second time a year later. When the Nazis seized power in 1933, Schönberg left Germany, where he held a professorship, and went to Paris with his family.

In Paris, he returned to Judaism, having previously converted from Judaism to Protestantism. His fellow artist, Marc Chagall (1887-1985), was a witness to the ceremony.

Later in 1933, the composer emigrated to the USA. "The Enigma of Modern Music Arrives," read the headline of a leading music magazine at the time.

After teaching in New York and Boston, Schönberg moved to Los Angeles, and eventually became a US citizen.

Schönberg's influence on 20th-century music was immense. The development of compositional technique and music theory — from atonality to the 12-tone technique to serial and finally to electronic music — all of this can be traced back to Schönberg.

The list of his students reads like a who's who of modern music history.

However, Schönberg never appealed to the taste of the general public, even though he yearned for it: "There is nothing I long for more intensely than to be taken for a better sort of Tchaikovsky — for heaven's sake: a bit better, but really that's all," he wrote to a friend in 1947. "Or if anything more, that people should know my tunes and whistle them."

This article was originally published in German.