The archives were founded through a donation of documents and funds by the German collector, historian and musicologist Hans Moldenhauer, in honour of his wife Rosaleen Moldenhauer.
The original bequest, consisting of over 3,500 documents, constituted the most comprehensive collection of original musical manuscripts ever accumulated. The collection spans musical periods from the Middle Ages through the 20th century, and includes original musical manuscripts by 57 of the foremost western composers, from Bach, Bartók, Beethoven and Brahms, via Mahler, Mendelssohn and Mozart, to Schubert, Schoenberg and Webern.
Since 1987, the Moldenhauer Archives have grown to many thousands of items that are now housed in nine institutions around the world:
in the United States, at the Library of Congress, Harvard University, Northwestern University, Washington State University, and Whitworth College; in Basel, Switzerland, at the Paul Sacher Foundation; in Zürich, Switzerland, at the Zentralbibliothek; in Munich, Germany, at the Bayerische Staatsbibliothek; and in Vienna, Austria, at the Stadtarchiv und Oesterreichische Nationalbibliothek.
