The music you will find here is from an uncataloged collection of individual sheet music – from song sheets to solo piano and violin sonatas – housed at the UWM Libraries Music Collection. Only music that is in the public domain, i.e., written prior to 1923, has been digitized. Likewise, only music not already digitized and available through another collection is included here.
If you do not find the music that you are looking for here, and are certain that it is in the public domain, here are few other digital collections to check.
The Lester S Levy Collection at Johns Hopkins University – over 29,000 pieces of American popular music spanning from 1780 to 1980. Its strength is its thorough documentation of nineteenth-century America through popular music. http://levysheetmusic.mse.jhu.edu/
The American Memory Project at the Library of Congress – a digital record that documents the American experience through creativity in written and spoken words, sound recordings, still and moving images, prints, maps, and sheet music. http://memory.loc.gov/ammem/index.html
The Sheet Music Consortium – the work of a group of libraries whose goal is to build an open collection of digitized sheet music. http://digital2.library.ucla.edu/sheetmusic/
The Music Collection’s website has links to more sources of legally available digital music. You will find that here https://uwm.edu/libraries/music/