After the latter contract was not renewed in 1923, he lived in Cologne as a freelance composer and conductor. He wrote major works for orchestra from 1917 and finally also the operaThe Basque Venus based on a libretto by his wife Lini Wetzlernée Dienstbach (1876–1933).[11]
In 1929, he moved toBrissago, in 1932 toBasel, where he lectured in 1933, and then toAscona. In Germany, he was banned from performing in 1935 because of his Jewish origins. After the outbreak of war, he left Switzerland and settled in New York in 1940, where he died on 29 May 1943 at the age of 72.
His estate has been in theZentralbibliothek Zürich since 2006 and contains, in addition to music autographs and writings, around 10,000 letters, 6000 reviews and photographs.
Aerni, Heinrich (2015).Zwischen USA und Deutschem Reich Hermann Hans Wetzler (1870–1943) ; Dirigent und Komponist (in German). Kassel, Base, lLondon, New York, NY, Praha: Bärenreiter.ISBN978-3-7618-2358-3.OCLC915163547.
