The Gui Mombaerts Papers, spanning the years 1922-1980, comprise two boxes. They include biographical material, vitae, press releases, clippings, and interviews. Considerable additional biographical information is available in the newspaper reviews of Mombaerts' musical performances (Box 2, Folders 1-6). One folder of scattered correspondence consists primarily of notes of appreciation from individuals who attended concerts given by Mombaerts. A second folder of correspondence includes letters written by Mombaerts' students on the occasion of his retirement in 1971.
The bulk of the papers consist of concert programs and newspaper clippings of reviews of performances given by Mombaerts spanning the period 1922-1980. The programs are divided into sections announcing Mombaerts' European concerts and his North American concerts. Each group of programs is arranged chronologically. The programs are for both concerts given by Mombaerts as a soloist and with other musicians; most notably William Primrose and the Belgian Piano-String Quartet. The newspaper reviews are similarly divided into European and North American sections and are likewise arranged chronologically within each section. Both programs and reviews detailing his European concert career are in a variety of foreign languages, including French, German, Italian, and Polish. Mombaerts' translations of some of the reviews are included with the reviews.