Over 760 letters and postcards written between [1948] and 1972 by the composer and musicologist Egon Wellesz (1885-1974), with a few wholly or partly by his wife, Emmy (1889-1987) and almost all addressed to their daughter Elizabeth (1912–1995), who in 1961 became Mrs Kessler. The occasional letter is addressed to Elizabeth's husband Charles and several to them jointly. One letter (from 1949) is addressed to his son-in-law, Dr Kary Pole, who married the Wellesz's other daughter Magdalena. There also a few letters from other people or copies of Wellesz's letters to others. The earliest letter of 1940 is from Elizabeth (Lisi) to her father.

The letters, usually signed 'Pepi' or 'P.', tell of many Oxford events and personalities, occasions elsewhere as well as chronicle Wellesz's own compositional activity and performances of his works. The letters are mostly written from Oxford but also other places he visited. A few letters are present only in photocopy, with the location of the original noted. Some letters from the 1950s bear a stamp 'Alliierte Zensurstelle' with various numbers.