The extensive files of correspondence contain mostly letters to, but also some letters from Lennox and Freda Berkeley.
The files include correspondence between Lennox and Freda, and letters from Lennox and Freda to cousin Yvonne Berkeley and family friend Sandy Walton, and from Lennox to Britten.
There are letters and cards to Lennox and Freda from many correpondents, including composers, musicians, singers, artists, writers, academics, Roman Catholics, and other figures and members of society.
The files include correpondence from Auden, Georges Auric, Betty Askwith, Patrick Balfour Lord Kinross, Conrad Beck, Sophie Behrens, Michael, Julian and Nicholas Berkeley, Yvonne Berkeley, Arthur and Trudy Bliss, Charlotte Bonham Carter, Nadia Boulanger, Julian Bream, Benjamin Britten, Roger Butler, Sir Hugh and Margaret Casson, Diana Cooper, Stewart Craggs, Janet Craxton, Clifford Curzon, Adrian Daintrey, Robert Gathorne-Hardy, Lord and Lady Gladwyn, Cecil Gould, Duncan Grant, Hans Gronau, Charles Groves, Alec Guinness, Derek Hill, Anne and Heywood Hill, Fr Anthony Hollings, Anthony and Lily Hornby, Helene Kahn Casella, Hans Keller, James Lees-Milne, John Lloyd, Wyndham Lloyd, Laurie Lee, Raymond Leppard, Nina Lucas, Lutosławski, Sir John Manduell, Rolland Manuel, Yehudi Menuhin, John Julius Norwich, Burnett Pavitt, Peter Pears, Camilla and Andrzej Pnufnik, Poulenc, Priaulx Rainier, Desmond Shawe-Taylor, Janet and Reynolds Stone, Patrick, Hugh and Alexandra Trevor-Roper, Brigid Utley, Sebastian Walker, Sandy Walton, William and Susana Walton, Ursula Vaughan Williams, Gordon Wheeler and Malcolm Williamson.
The files also include messages received on the occasions of the premiere of Nelson, Lennox's 70th and 75th birthdays and knighthood, and letters of condolence on Lennox's death. There is also correspondence between Lennox Berkeley's parents and other members of the Berkeley and Harris families.
The correspondence files contain mostly letters and cards, but also some press cuttings, obituaries, orders of service for services of thanksgiving, programmes, pamphlets, photographs and other items. Some of the correspondence is sorted and filed by surname of the correspondent, or occasionally by the surname of the person about whom an item relates, such as an obituary. Some letters are currently unsorted in general correspondence files.