Some years later in 1926, the composer put her late husband's first name in front of her own, going by Albert Maria Herz in order to help her to gain a foothold in her male-dominated profession. After her husband's death, Maria eventually resumed her composition lessons, first with August von Othegraven (1864-1946) and Hermann Hans Wetzler (1870-1943), and from 1927 with the distinguished composer Philipp Jarnach (1892-1982). Her new works began to be performed regularly, culminating in the premiere of the Four Little Orchestral Movements op. 8 on 15 October 1928 at the Cologne Gürzenich under Hermann Abendroth.
The period from 1920 to 1935 was her most fruitful creative period, during which she produced a remarkable body of compositions. Maria Herz maintained a lively exchange with many of the leading musicians of the day. Her circle of acquaintances included the Budapest String Quartet, the Quartet di Roma, the singer Ilona Durigo, the baritone Hermann Schey, the cellists Gregor Piatigorsky, Emanuel Feuermann and Gaspar Cassadó, and the conductors Hermann Abendroth, Peter Raabe and Hans Rosbaud. Among her friends was the conductor Otto Klemperer, first Kapellmeister of the Cologne Opera. Her list of works includes numerous songs for voice and piano (some cycles were orchestrated), chamber music, solo concertos for piano and cello, as well as choral and orchestral works. These works range in style from late Romanticism to early modernism and are still often highly demanding for the performers.
When the Nazis came to power in 1933, Jewish composers were banned from performing. Once again, the Herz family were forced to leave Germany, leaving Maria and her children stateless for a year. Her birthplace of Cologne had become inhospitable for Jews, then covered in swastikas and antisemitic propaganda. She first took lodgings in Berlin, then in Trier, where one of her daughters ran a pottery workshop. Maria reached London in February 1935, but returned to Europe, this time to Switzerland, to change her address. Throughout this period, she was restless, moving between Paris, Lyon, Switzerland and back to Lyon. Realising that this was her only way out, she returned to England with her younger son Robert, where she lived in exile for almost ten years. Her other three children were scattered around the world: in Switzerland and the United States. Maria and Robert found refuge in Birmingham, the second largest city in the United Kingdom at the time.
In the winter of 1940, Maria moved into a house in King's Norton, in the south of Birmingham. She stayed there until 1945, living in wartime exile with her son. There, she wrote lectures on composers from different countries and periods. By 1934, Maria Herz had produced some 30 works - orchestral works and solo concertos, chamber music and piano songs. Yet, after 1935, she composed very little. In her last work, the Concerto for Piano, Flute and Strings, she adapted Baroque forms. Maria never explained as to why this was her last composition, but one thing is for certain: Maria Herz took the score of this concerto with her into exile and finished the piece, before never composing anything again. After the war, she emigrated with her son to be with her daughters in New York, where she died on 22 October 1950, aged 72, after a short, serious illness and was buried in Springfield, New Jersey.
Only five of Maria’s songs (1910, Stainer & Bell) and her arrangement of Bach's Chaconne for string quartet (1927, Simrock No. 774a, b) were published during her lifetime; other compositions are survived in manuscripts. Her estate remained with her descendants in the United States, where most of her music lay forgotten in drawers, until her grandson Albert Herz transferred it to Zurich, Switzerland in 1995 and donated it to the Zurich Central Library. Since October 2015, Maria Herz's legacy has become a permanent part of the ‘Legacy Collections’ of the music department of the Zentralbibliothek Zürich.
In recent years, Maria Herz's music has been rediscovered, and her works are being performed again. Her final composition was premiered 85 years later - in autumn 2020 in Zurich, where Maria Herz's grandson Albert Herz lives today. He was only four years old when he saw his grandmother for the first and last time in 1949, and strives to keep her compositions, and memory alive for future generations.