„My time will come after my death” 
Zemlinsky to his wife Louise

Louise Zemlinsky had to experience a further shattering stroke of fate after the death of her brother and her husband. In 1945 she was informed in a telegram that her mother and aunt had most probably been murdered in a concentration camp.

Left completely to her own devices she made attempts already during the 1940s to promote Zemlinsky's works in the music world but the response was discouraging. From 1945 she again lived in New York and devoted herself entirely to singing and painting. It was not until the late 1960s, when Zemlinsky was gradually being rediscovered, that her husband's legacy increasingly became her principal task in life. Until a highly advanced age she committed herself to ensuring that the research and performance of his music, especially regarding copyright matters, had a serious basis and created a widespread impact. She was given considerable help by the Austrian Cultural Institute and its director at the time Peter Marboe. He also ensured that in 1985 at Louise's request Zemlinsky's urn was transferred to Austria and interred in an honorary grave in Vienna's Central Cemetery.

However, the main focus of interest was the need to provide long-term security in the form of an institution for promoting his heritage. Louise donated a considerable sum of money to the College of Music at the University of Cincinnati. The donation was used to set up a composition and instrumental competition both bearing Zemlinsky's name and which have been organised since the 1990s at this institute where Walter Levin, a great admirer of Zemlinsky, taught for many years. Nevertheless the most important initiative taken by Louise was the setting up of the Alexander Zemlinsky Foundation at the Society of the Friends of Music in Vienna that was founded in 1989 using a large donation from her funds. The purpose of the foundation, whose chairman is Peter Dannenberg, is to "promote and disseminate the works of Alexander Zemlinsky as well as to analyse his life, his impact and his works". Members of the Foundation Committee also include Gerd Albrecht, Thomas Angyan, Christoph von Dohnányi, James Levine, Peter Marboe and Peter Ruzicka.

Louise died in 1992 in New York. All the rights to Zemlinsky's music were transferred to the foundation. Throughout his life Vienna did not make things easy for Zemlinsky. Now, fifty years after his death, his heritage has at least „found its logical home” (Peter Marboe).