The Dorabella cipher

The note has three lines of 29, 31 and 27 symbols. Each symbol is one, two or three nested semicircles whose open side faces one of eight directions at 45-degree steps, giving 24 possible symbols, of which 20 appear; a small dot follows the fifth symbol of the last line⁠[4]⁠[2]. The orientation of some symbols is ambiguous in the facsimile, and published transcriptions differ at a few places; Hauer and colleagues built a majority transcription from five, which this project uses⁠[4]⁠[5].

Elgar used the same symbols elsewhere. In April 1886 he pencilled 18 of them into a Crystal Palace concert programme beside a musical example from Liszt's Les Préludes; they appear again in an exercise book of about 1920, with diagrams like clock faces; and on a card headed "Cryptogram" that belongs with his working of a cipher challenge printed in the Pall Mall Magazine in 1896⁠[6]⁠[7]⁠[8]. The programme and the exercise book were reported in 2007 to be at the Elgar Birthplace Museum⁠[7].

Elgar was a lifelong maker of puzzles, puns and ciphers; Dora's memoir opens its appendix by saying so, and his 1896 work on the Pall Mall challenge shows he could break a cipher as well as make one⁠[1]⁠[6]. The exercise-book pages are the strongest clue to the system: a commenter on Nick Pelling's site reports that they pair the semicircle alphabet with test phrases such as "A very old cipher", "Do you go to London" and "Marco Elgar", which suggests a key that assigns letters to the symbols in a fixed rotational order⁠[9]. If so, the system is a simple alphabet of Elgar's devising, and the difficulty lies in the message, not the cipher.

The frequencies of the 20 symbols resemble a letter distribution in a short English text⁠[10]. The Liszt fragment has been read as "GETS YOU TO JOY, AND HYSTERIOUS" (Anthony Thorley, 1977), a reading Jerrold Northrop Moore printed in his biography of Elgar but which others find unconvincing⁠[7]⁠[8].

Klaus Schmeh applied Helen Fouché Gaines's manual methods for monoalphabetic substitution (vowel detection, digram analysis, consonant lining) to the cipher and to a control text of the same length. Vowel detection worked well on the control and gave candidate vowels for Dorabella, but no reading⁠[10].

Hauer, Choi, Sundar, Hindle, Smallwood and Kondrak ran state-of-the-art automatic solvers that reliably break 87-letter English substitutions; none produced readable text from Dorabella. A ciphertext language identifier ranked English as the most likely underlying language; character-model classifiers placed the cipher closer to language than to music; and Dorabella has 13 pairs of mirrored symbols where random English enciphered with these symbols has 3.6 on average, which happens by chance about one time in a thousand. They read the mirrored pairs as structure, perhaps a way of writing double letters, and as evidence against a meaningless hoax⁠[4]. Viktor Wase showed that decipherment algorithms solve English and Latin substitutions as short as Dorabella and fail on Dorabella itself, and concluded it is not a monoalphabetic substitution in either language⁠[11].

In 2007, for the 150th anniversary of Elgar's birth, the Elgar Society ran a Dorabella competition. Several entries came in and none was accepted: entries that matched symbols to letters "invariably ended up with a fairly arbitrary sequence of letters" read as "a disconnected chain of bizarre utterances"⁠[2].

Eric Sams proposed in 1970 a substitution reading in which phonetic shorthand turns 87 symbols into 109 letters: "Starts: Larks! It's chaotic, but a cloak obscures my new letters..."⁠[12]. Later claims include simple substitutions with nulls (Richard Henderson, 2011; Tim Roberts, about 2012) and a reading by Wayne Packwood (2020) that rearranges the text by its dots and shifts each symbol's value without a stated rule⁠[2]⁠[13]. Each needs free choices that allow other readings equally well, and none has been accepted⁠[3]⁠[9].

Three broader readings remain. The note is English in Elgar's alphabet but not a plain substitution: it may use phonetic spelling, abbreviations, private jokes, double letters marked by mirroring, or a reading order other than line by line⁠[4]⁠[12]. It encodes music: the eight orientations as notes of a scale and the arc count as a modifier, a reading proposed by Javier Atance and tested, without support, by Hauer and colleagues⁠[2]⁠[4]⁠[5]. Or it means nothing that could be decoded, a joke made to look like a cipher; the non-random mirroring weighs against this⁠[4].

A key in Elgar's hand that maps his semicircle alphabet to letters, tested on the Liszt fragment and the exercise-book phrases, and then producing a sensible English text from Dorabella without further free choices, would settle it. High-resolution images of the exercise book, the Cryptogram card and the 1886 programme, published with transcriptions, are the most useful single step; the 1937 facsimile is the only image of Dorabella itself, so any lost original resurfacing would also resolve the ambiguous orientations.