cryptography Cryptography, or cryptology (from "hidden, secret"; and ''graphein'', "to write", or ''-logy, -logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of Adversary (cryptography), ...

, a music cipher is an

algorithm In mathematics and computer science, an algorithm () is a finite sequence of Rigour#Mathematics, mathematically rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algo ...

for the

encryption In Cryptography law, cryptography, encryption (more specifically, Code, encoding) is the process of transforming information in a way that, ideally, only authorized parties can decode. This process converts the original representation of the inf ...

of a plaintext into musical symbols or sounds. Music-based ciphers are related to, but not the same as

musical cryptogram A musical cryptogram is a cryptogrammatic sequence of musical symbols which can be taken to refer to an extra-musical text by some 'logical' relationship, usually between note names and letters. The most common and best known examples result fr ...

s. The latter were systems used by composers to create musical themes or motifs to represent names based on similarities between letters of the alphabet and musical note names, such as the

BACH motif In music, the BACH motif is the motif (music), motif, a succession of note (music), notes important or characteristic to a musical composition, piece, ''B flat, A, C, B natural''. In Letter notation, German musical nomenclature, in whi ...

, whereas music ciphers were systems typically used by cryptographers to hide or

encode The Encyclopedia of DNA Elements (ENCODE) is a public research project which aims "to build a comprehensive parts list of functional elements in the human genome." ENCODE also supports further biomedical research by "generating community resourc ...

messages for reasons of secrecy or espionage.

Types

There are a variety of different types of music ciphers as distinguished by both the method of encryption and the musical symbols used. Regarding the former, most are simple

substitution cipher In cryptography, a substitution cipher is a method of encrypting in which units of plaintext are replaced with the ciphertext, in a defined manner, with the help of a key; the "units" may be single letters (the most common), pairs of letters, t ...

s with a one-to-one correspondence between individual letters of the alphabet and a specific musical note. There are also historical music ciphers that utilize homophonic substitution (one-to-many), polyphonic substitution (many-to-one), compound cipher symbols, and/or cipher keys; all of which can make the enciphered message more difficult to break. Regarding the type of symbol used for substitution, most music ciphers utilize the pitch of a

musical note In music, notes are distinct and isolatable sounds that act as the most basic building blocks for nearly all of music. This musical analysis#Discretization, discretization facilitates performance, comprehension, and musical analysis, analysis. No ...

as the primary cipher symbol. Since there are fewer notes in a standard musical scale (e.g., seven for

diatonic scale In music theory a diatonic scale is a heptatonic scale, heptatonic (seven-note) scale that includes five whole steps (whole tones) and two half steps (semitones) in each octave, in which the two half steps are separated from each other by eith ...

s and twelve for

chromatic scale The chromatic scale (or twelve-tone scale) is a set of twelve pitches (more completely, pitch classes) used in tonal music, with notes separated by the interval of a semitone. Chromatic instruments, such as the piano, are made to produce the ...

s) than there are letters of the alphabet, cryptographers would often combine the note name with additional characteristics––such as

octave In music, an octave (: eighth) or perfect octave (sometimes called the diapason) is an interval between two notes, one having twice the frequency of vibration of the other. The octave relationship is a natural phenomenon that has been referr ...

clef A clef (from French: 'key') is a musical symbol used to indicate which notes are represented by the lines and spaces on a musical staff. Placing a clef on a staff assigns a particular pitch to one of the five lines or four spaces, whic ...

––to create a complete set of cipher symbols to match every letter. However, there are some music ciphers which rely exclusively on rhythm instead of pitch or on relative

scale degree In music theory, the scale degree is the position of a particular note on a scale relative to the tonic—the first and main note of the scale from which each octave is assumed to begin. Degrees are useful for indicating the size of intervals ...

names instead of absolute pitches.

Musical steganography

Music ciphers often have both cryptographic and steganographic elements. Simply put, encryption is scrambling a message so that it is unreadable; steganography is hiding a message so no knows it is even there. Most practitioners of music ciphers believed that encrypting text into musical symbols gave it added security because, if intercepted, most people would not even suspect that the sheet music contained a message. However, as

Francesco Lana de Terzi Francesco Lana de Terzi (1631 in Brescia, Lombardy – 22 February 1687, in Brescia, Lombardy) was an Italian Jesuit priest, mathematician, naturalist and aeronautics pioneer. Having been professor of physics and mathematics at Brescia, he fi ...

notes, this is usually not because the resulting cipher melody appears to be a normal piece of music, but rather because so few people know enough about music to realize it is not ("ma gl'intelligenti di musica sono poci"). A message can also be visually hidden within a page of music without actually being a music cipher. William F. Friedman embedded a secret message based on Francis

Bacon's cipher Bacon's cipher or the Baconian cipher is a method of steganographic message encoding devised by Francis Bacon in 1605. In steganography, a message is concealed in the presentation of text, rather than its content. Baconian ciphers are categorized ...

into a sheet music arrangement of Stephen Foster's "My Old Kentucky Home" by visually altering the appearance of the

note stem In musical notation, stems are the "thin, vertical line (geometry), lines that are directly connected to the notehead, otehead." Stems may point up or down. Different-pointing stems indicate the voice (music), voice for polyphonic music writ ...

s. Another steganographic strategy is to musically encrypt a plaintext, but hide the message-bearing notes within a larger musical score that requires some visual marker that distinguishes them from the meaningless null-symbol notes (e.g., the cipher melody is only in the tenor line or only the notes with stems pointing down). Notes Amadi 41v

The cipher manuscript from Agostino Amadi there is a musical score in 41v with a pseudo-letter ciphered in it, which is an imaginary letter that Venice writes to Charles V.

Italian historian Paolo Preto Italian(s) may refer to: * Anything of, from, or related to the people of Italy over the centuries ** Italians, a Romance ethnic group related to or simply a citizen of the Italian Republic or Italian Kingdom ** Italian language, a Romance languag ...

. "...The emperor sent to prince Gritti, with whom he had been familiar for a long time, a music score that looked like a madrigal....The prince summoned Willaert and the other musicians and asked them to play the melody sent to them by emperor Charles V. When Willaert and the others carefully studied the score, they were unable to play it and confessed they could not understand it."

Diatonic substitution ciphers

Diatonic music ciphers utilize only the seven basic note names of the diatonic scale: ''A, B, C, D, E, F'', and ''G''. While some systems reuse the same seven pitches for multiple letters (e.g., the pitch ''A'' can represent the letters A, H, O, or V), most algorithms combine these pitches with other musical attributes to achieve a one-to-one mapping. Perhaps the earliest documented music cipher is found in a manuscript from 1432 called "The Sermon Booklets of Friar Nicholas Philip." Philip's cipher uses only five pitches, but each note can appear with one of four different rhythmic durations, thus providing twenty distinct symbols. A similar cipher appears in a 15th-century British anonymous manuscript as well as in a much later treatise by Giambattista della Porta. In editions of the same treatise (''

De Furtivis Literarum Notis ''De Furtivis Literarum Notis'' (''On the Secret Symbols of Letters'') is a 1563 book on cryptography written by Giambattista della Porta. The book includes three sets of cypher discs for coding and decoding messages, a substitution cipher impro ...

''), Porta also presents a simpler cipher which is much more well-known. Porta's music cipher maps the letters A through M (omitting J and K) onto a stepwise, ascending, octave-and-a-half scale of

whole note A whole note (American) or semibreve (British) in musical notation is a single note equivalent to or lasting as long as two half notes or four quarter notes. Description The whole note or semibreve has a note head in the shape of a hollow ov ...

s (semibreves); with the remainder of the alphabet (omitting V and W) onto a descending scale of

half note In music, a half note (American) or minim (British) is a Musical note, note played for half the duration of a whole note (or semibreve) and twice the duration of a quarter note (or crotchet). It was given its Latin name (''minima'', meaning "le ...

s (minims). Since alphabetic and scalar sequences are in such close step with each other, this is not a very strong method of encryption, nor are the melodies it produces very natural. Nevertheless, one finds slight variations of this same method employed throughout the 17th and 18th centuries by

Daniel Schwenter Daniel Schwenter (Schwender) (31 January 1585 – 19 January 1636) was a German Orientalist, mathematician, inventor, poet, and librarian. Biography Schwenter was born in Nuremberg. He was professor of oriental languages and mathematics at ...

(1602),

John Wilkins John Wilkins (14 February 1614 – 19 November 1672) was an English Anglican ministry, Anglican clergyman, Natural philosophy, natural philosopher, and author, and was one of the founders of the Royal Society. He was Bishop of Chester from 1 ...

(1641),

Athanasius Kircher Athanasius Kircher (2 May 1602 – 27 November 1680) was a German Society of Jesus, Jesuit scholar and polymath who published around 40 major works of comparative religion, geology, and medicine. Kircher has been compared to fellow Jes ...

(1650), Kaspar Schott (1655),

Philip Thicknesse Captain Philip Thicknesse (1719 – 23 November 1792) was a British Army officer and writer who was a friend of the artist Thomas Gainsborough. He wrote several travel guides. Early life Philip Thicknesse was born in Staffordshire, England, so ...

(1722), and even the British Foreign Office (ca. 1750).

Chromatic substitution ciphers

Music ciphers based on the

provide a larger pool of note names to match with letters of the alphabet. Applying sharps and

flats Flat or flats may refer to: Architecture * Apartment, known as a flat in the United Kingdom, Ireland, and other Commonwealth countries Arts and entertainment * Flat (music), a symbol () which denotes a lower pitch * Flat (soldier), a two-dimens ...

to the seven diatonic pitches yields twenty-one unique cipher symbols. Since this is obviously still less than a standard alphabet, chromatic ciphers also require either a reduced letter set or additional features (e.g., octave register or duration). Most chromatic ciphers were developed by composers in the 20th Century when fully chromatic music itself was more common. A notable exception is a cipher attributed to the composer

Michael Haydn Johann Michael Haydn (; 14 September 1737 – 10 August 1806) was an Austrian composer of the Classical period (music), Classical period, the younger brother of Joseph Haydn. Life Michael Haydn was born in 1737 in the Austrian village of Rohra ...

(brother of the more famous

Joseph Haydn Franz Joseph Haydn ( ; ; 31 March 173231 May 1809) was an Austrian composer of the Classical period (music), Classical period. He was instrumental in the development of chamber music such as the string quartet and piano trio. His contributions ...

). Haydn's algorithm is one of the most comprehensive with symbols for thirty-one letters of the

German alphabet The modern German alphabet consists of the twenty-six letters of the ISO basic Latin alphabet: German uses letter-diacritic combinations (Ä, Ä/ä, Ö, Ö/ö, Ü, Ü/ü) using the Umlaut (diacritic), umlaut and one ligature (ß, ẞ/ß (ca ...

, punctuations (using rest signs), parentheses (using

s), and word segmentation (using bar lines). However, because many of the pitches are enharmonic equivalents, this cipher can only be transmitted as visual steganography, not via musical sound. For example, the notes ''C-sharp'' and ''D-flat'' are spelled differently, but they sound the same on a piano. As such, if one were listening to an enciphered melody, it would not be possible to hear the difference between the letters K and L. Furthermore, the purpose of this cipher was clearly not to generate musical themes that could pass for normal music. The use of such an extreme chromatic scale produces wildly dissonant,

atonal Atonality in its broadest sense is music that lacks a tonal center, or key. ''Atonality'', in this sense, usually describes compositions written from about the early 20th-century to the present day, where a hierarchy of harmonies focusing on ...

melodies that would have been obviously atypical for Haydn's time.

20th-century ciphers

Although chromatic ciphers did not seemed to be favored by cryptographers, there are several 20th-century composers who developed systems for use in their own music:

Arthur Honegger Arthur Honegger (; 10 March 1892 – 27 November 1955) was a Swiss-French composer who was born in France and lived a large part of his life in Paris. Honegger was a member of Les Six. For Halbreich, '' Jeanne d'Arc au bûcher'' is "more even ...

Maurice Duruflé Maurice Gustave Duruflé (; 11 January 1902 – 16 June 1986) was a French composer, organist, musicologist, and teacher. Life and career Duruflé was born in Louviers, Eure in 1902. He attended Rouen Cathedral Choir School from 1912 to 1918, ...

, Norman Cazden,

Olivier Messiaen Olivier Eugène Prosper Charles Messiaen (, ; ; 10 December 1908 – 27 April 1992) was a French composer, organist, and ornithology, ornithologist. One of the major composers of the 20th-century classical music, 20th century, he was also an ou ...

, and

Jacques Chailley Jacques Chailley (24 March 1910 – 21 January 1999) was a French musicologist and composer. Alain Lompech, "Jacques Chailley, musicologue-praticien et infatigable chercheur", ''Consociatio internationalis musicæ sacræ, Musicæ sacræ ministeriu ...

. Similar to Haydn's cipher, most likewise match the alphabet sequentially onto a chromatic scale and rely on octave register to extend to twenty-six letters. Only Messiaen's appears to have been thoughtfully constructed to meet the composer's aesthetic goals. Although he also utilized different octave registers, the letters of the alphabet are not mapped in scalar order and also have distinct rhythmic values. Messiaen called his musical alphabet the ''langage communicable'', and used it to embed extra-musical text throughout his organ work Méditations sur le Mystère de la Sainte Trinité.

Compound motivic ciphers

In a compound substitution cipher, each single plaintext letter is replaced by a block of multiple cipher symbols (e.g., 'a' = EN or 'b' = WJU). Similarly, there are compound music ciphers in which each letter is represented by a musical motive with two or more notes. In the case of the former, the compound symbols are to make

frequency analysis In cryptanalysis, frequency analysis (also known as counting letters) is the study of the frequency of letters or groups of letters in a ciphertext. The method is used as an aid to breaking classical ciphers. Frequency analysis is based on th ...

more difficult; in the latter, the goal is to make the output more musical. For example, in 1804, Johann Bücking devised a compound cipher which generates musical compositions in the form of a

minuet A minuet (; also spelled menuet) is a social dance of French origin for two people, usually written in time. The English word was adapted from the Italian ''minuetto'' and the French ''menuet''. The term also describes the musical form tha ...

in the key of G Major. Each letter of the alphabet is replaced by a measure of music consisting of a stylistically typical motive with three to six notes. After the plaintext is enciphered, additional pre-composed measures are appended to the beginning and end to provide a suitable musical framing. A few years earlier,

Wolfgang Amadeus Mozart Wolfgang Amadeus Mozart (27 January 1756 – 5 December 1791) was a prolific and influential composer of the Classical period (music), Classical period. Despite his short life, his rapid pace of composition and proficiency from an early age ...

appears to have employed a similar technique (with much more sophisticated musical motives), although more likely intended as a parlor game than an actual cipher. Since the compound symbols are musically meaningful motives, these ciphers could also be considered similar to

codes In communications and information processing, code is a system of rules to convert information—such as a letter, word, sound, image, or gesture—into another form, sometimes shortened or secret, for communication through a communication ch ...

. Friedrich von Öttingen-Wallerstein proposed a different type of compound music cipher modeled after a polybius square cipher. Öttingen-Wallerstein used a 5x5 grid containing the letters of the alphabet (hidden within the names of angels). Instead of indexing the rows and columns with coordinate numbers, he used the solfege syllables Ut, Re, Mi Fa, and Sol (i.e., the first five degrees of a diatonic scale). Each letter, therefore, becomes a two-note melodic motive. This same cipher appears in treatises by Gustavus Selenus (1624) and Johann Balthasar Friderici (1665) (but without credit to the earlier version of Öttingen-Wallerstein).

Music ciphers with keys

Because Öttingen-Wallerstein's cipher uses relative

scale degrees In music theory, the scale degree is the position of a particular note on a scale relative to the tonic—the first and main note of the scale from which each octave is assumed to begin. Degrees are useful for indicating the size of intervals ...

, rather than fixed note names, it is effectively a

polyalphabetic cipher A polyalphabetic cipher is a substitution cipher, substitution, using multiple substitution alphabets. The Vigenère cipher is probably the best-known example of a polyalphabetic cipher, though it is a simplified special case. The Enigma machine i ...

. The same enciphered message could be transposed to a different musical key––with different note names––and still retain the same meaning. The musical key literally becomes a cipher key (or cryptovariable), because the recipient needs that additional information to correctly decipher the melody. Öttingen-Wallerstein inserted rests as cipherkey markers to indicate when a new musical key was needed to decrypt the message.

used a more conventional text-string cryptovariable, to add security to a very straightforward 'Porta-style' music cipher (1670). Similar to a

Vigenère cipher The Vigenère cipher () is a method of encryption, encrypting alphabetic text where each letter of the plaintext is encoded with a different Caesar cipher, whose increment is determined by the corresponding letter of another text, the key (crypt ...

, a single-letter cipher key shifts the position of the plaintext alphabet in relation to the sequence musical cipher symbols; a multi-letter key word shifts the musical scale for each letter of the text in a repeating cycle. A more elaborate cipherkey algorithm was found in an anonymous manuscript in Port-Lesney, France, most likely from the mid-18th century. The so-called 'Port-Lesney' music cipher uses a mechanical device known as an

Alberti cipher disk Alberti may refer to: Leon Battista Alberti, the Renaissance architect Places * Alberti Partido, a partido of Buenos Aires Province, Argentina * Alberti, Buenos Aires, the main town of the partido * Alberti (Buenos Aires Underground), a railwa ...

There are two rotating disks: the outer disk contains two concentric rings (one with

time signature A time signature (also known as meter signature, metre signature, and measure signature) is an indication in music notation that specifies how many note values of a particular type fit into each measure ( bar). The time signature indicates th ...

s and the other with letters of the alphabet); the inner disk has a ring of compound musical symbols, and a small inner circle with three different

signs. The disks are rotated to align the letters of the alphabet with compound musical symbols to encrypt the message. When the melody is written out on a music staff, the corresponding clef and time signature are added to the beginning to indicate the cipher key (which the recipient aligns on their disk to decipher the message). This particular music cipher was apparently very popular, with a dozen variations (in French, German, and English) appearing throughout the 18th and 19th centuries. Solfa Cipher interface

The more recent Solfa Cipher combines some of the above cryptovariable techniques. As the name suggests, Solfa Cipher uses relative solfege degrees (like Öttingen-Wallerstein) rather than fixed pitches, which allows the same encrypted message to be transposable to different musical keys. Since there are only seven scale degrees, these are combined with a rhythmic component to create enough unique cipher symbols. However, instead of absolute note lengths (e.g., quarter note, half note, etc.) that are employed in most music ciphers, Solfa Cipher uses relative

metric Metric or metrical may refer to: Measuring * Metric system, an internationally adopted decimal system of measurement * An adjective indicating relation to measurement in general, or a noun describing a specific type of measurement Mathematics ...

placement. This type of ''tonal-metric'' cipher makes the encrypted melody both harder to break and more musically natural (i.e. similar to common-practice tonal melodies). To decrypt a cipher melody, the recipient needs to know in which musical key and with what rhythmic unit the original message was encrypted, as well as the clef sign and metric location of the first note. The cipher key could also be transmitted as a date by using ''Solfalogy'', a method of associating each unique date with a tone and modal scale. To further confound interceptors, the transcribed sheet music could be written with a decoy clef, key signature, and time signature. The musical output, however, is a relatively normal, simple, singable tune in comparison to the disjunct, atonal melodies produced by fixed-pitch substitution ciphers.

References

Sources

*Alberti, Leon Battista. 1467. De Cifris. Biblioteca Nazionale Marciana. Cod. Marc. Lat. XIV 32 (4702) f. 1r. (sec. XVI). *Arnold, George. 1862. The Magician's Own Book. New York: Dick & Fitzgerald. *Bacon, Francis. 1605. The Proficience and Advancement of Learning Divine and Humane. Oxford *Belloni, Gabriella. 1982. "Conoscenza magica e ricerca scientifica in G. B. Della Porta". Criptologia / Giovan Battista Della Porta. Rome: Centro internazionale di studi umanistici *Bernard, Francis. c.1400. Sloan MS 351, British Library. *Bertini, A. 1811. Stigmatographie ou l'art d'écrire avec des points. France: Martinet. *Boethius, Anicius Manlius Severinus. c.524. De Institutione Musica. Translated by Calvin Bower, 1989, Fundamentals of Music (ed. C. Palisca), Yale University Press. *Bücking, Johannn. J. 1804. Anweisung zur geheimen Correpondenz. Heinrich Georg Albreht. *Cazden, Norman. 1961a. "Staff Notation as a Non-Musical Communications Code," Perspectives of New Music, Vol. 5, No. 1, 113–128 *Cazden, Norman. 1961b. "How to Compose Non-Music," Perspectives of New Music, Vol. 5, No. 2, 287–296 *Chailley, Jacques. 1981. "Anagrammes Musicales Et "langages Communicables"." Revue De Musicologie 67, no. 1: 69-80. doi:10.2307/928141. *Champour, MM. de and François Malepeyre. 1856. Nouveau manuel complet de la fabrication des encres telles. A la Librairie encyclopédique de Roret. *Code, David Løberg. 2023. "Can musical encryption be both? A survey of music-based ciphers." ''Cryptologia'' Volume 47 - Issue 4, https://doi.org/10.1080/01611194.2021.2021565 *Daverio, John. 2002. Crossing Paths: Schubert, Schumann, and Brahms. Oxford University Press. *Djossa, Christina Ayele. 2018. "With Music Cryptography, Composers Can Hide Messages in Their Melodies," Atlas Obscura. https://www.atlasobscura.com/articles/musical-cryptography-codes *Duruflé, Maurice. 1942. Prélude et fugue sur le nom d'Alain, Op. 7. *Écorcheville, Jules. 1909. "Homage à Joseph Haydn," Revue musicale S.I.M. Société internationale de musique. https://gallica.bnf.fr/ark:/12148/bpt6k5589273s/f51.item *Ernst, Thomas. 1996. “Schwarzweisse Magie. Der Schlussel zum dritten Buch der Steganographia des Trithemius.” Daphnis 25, Heft 1. *Friderici, Johann Balthasar. 1665. ''Cryptographia''. https://www.digitale-sammlungen.de/de/view/bsb10897282?page=193 *Gale, John. 1796. Gale's Cabinet of Knowledge. W. Kemmish. *Godwin, Francis. 1638. The Man in the Moone or A Discourse of a Voyage Thither by Domingo Gonsales. John Norton. *Guyot, Edme Gilles and Guillaume Germain Guyot. 1769. Recreations Sur Les Nombres. Gueffier. *Honegger, Arthur. 1928. Homage à Albert Roussel, H.69. Editions Salabert. *Hooper, William. 1794. Rational Recreations. B. Law and Son. *Jacob, Paul Lacroix. 1858. La cryptographie: ou, L'art d'écrire en chiffres. Adolphe Delahays. *Kircher, Athanasius. 1650. Musurgia Universalis. https://archive.org/details/bub_gb_97xCAAAAcAAJ/page/n389/mode/2up *Klüber, Johann Ludwig. 1808. Kryptographik. Cottaschen. https://archive.org/details/bub_gb_lqRAAAAAcAAJ/page/n543/mode/2up *Knowlson, James R. 1968. "A Note on Bishop Godwin's 'Man in the Moone:' The East Indies Trade Route and a 'Language' of Musical Notes." Modern Philology 65, no. 4: 357–61 *Kojima, Kenji. 2013. "Algorithmic Composition 'CiberTune'". http://kenjikojima.com/cipherTune/ *Lacombe, Jacques. 1792. Encyclopédie Méthodique: Des Amusemens Des Sciences Mathématiques Et Physiques. Chez Panckoucke *Langlais, Jean. 1976. Deuxième symphonie pour orgue 'Alla Webern' *McAvoy, Gary. 2021. The Vivaldi Cipher. Literati Editions. *Meister, Aloys. 1906. Die Geheimschrift im Dienste der päpstlichen Kurie von ihren Anfängen bis zum Ende des XVI Jarhhunderts. Schöningh. *Messiaen, Olivier. 1969. Méditations sur le mystère de la Sainte Trinité *Mozart, Wolfgang Amadeus. 1787. Music manuscript MS 253–01, Bibliothèque Nationale de France. https://catalogue.bnf.fr/ark:/12148/cb424728984 *New York Public Library, Manuscripts and Archives Division. 1916. "My Old Kentucky Home, Good Night" The New York Public Library Digital Collections. https://digitalcollections.nypl.org/items/bd9b1e30-8607-0131-ac72-58d385a7b928 *Noguchi, Hideo. 1990. "Mozart – Musical Game in C K.516f" Mitteilungen der Internationalen Stiftung Mozarteum 38, 89–101. *Öttingen-Wallerstein, Friedrich von. c.1600. ''Steganographia comitis''. https://diglib.hab.de/wdb.php?dir=mss/56-aug-4f *Philip, Nicholas. 1436. "The Sermon Booklets of Friar Nicholas Philip" MS Lat. th.d.I, Bodleian Library, Oxford. *Porta, Giambattista della. 1602. De Furtivis Literarum Notis. https://books.google.com/books?id=UIZeAAAAcAAJ *Porta, Giambattista della. 1606. De Occultis Literarum Notis. https://warburg.sas.ac.uk/pdf/noh4260.o11b2715108.pdf *Prince, Jon and Mark Schmuckler. 2014. "The Tonal-Metric Hierarchy: A Corpus Analysis," Music Perception, 31(3), 254–270. *Rettensteiner, Werigand. 1808. Biographische Skizze von Michael Haydn. *Reuter, Christoph. 2013. "Namadeus – Play Your Name with Mozarts Game (KV 516f). Musicpsychologie, Bd.23, 154-159. *Sams, Eric. 1966. "The Schumann Ciphers" The Musical Times, May 1966: 392–399. *Schooling, John Holt. 1896. “Secrets in Cipher I-IV”, Pall Mall Magazine, viii, 119–29, 245–56, 452–62, 608–18 *Schott, Kaspar. 1655. Schola Steganographica. https://books.google.com/books?id=XQNCAAAAcAAJ *Schwenter, Daniel. 1622. Steganologia & Steganographia Aucta. https://www.digitale-sammlungen.de/de/view/bsb11081558?page%3D325&sa=D&source=editors&ust=1623428284662000&usg=AOvVaw1bu67EE5i9j8vDKBVE6OjS *Selenius, Gustavus. 1624. Cryptomenytices et Cryptographiae libri IX. https://books.google.com/books?id=gc9TAAAAcAAJ *Shenten, Andrew. 2008. Olivier Messiaen's System of Signs: Notes Towards Understanding His Music. Ashgate Publishing. *Sudre, François. 1866. Langue Musicale Universelle. http://www.ifost.org.au/~gregb/solresol/sudre-book.pdf *Terzi, Francesco Lana de. 1670. ''Prodromo, ouero, Saggio di alcune inuentione nuoue, premesso all'arte maestra'' https://archive.org/details/prodromoouerosag00lana/page/n265/mode/1up *Theun, Johann Christophe. 1772. Neue physikalische und mathematische Belustigungen, Bey Berhard Kletts *Thicknesse, Philip. 1772. A treatise on the art of decyphering, and of writing in cypher. With an harmonic alphabet. W. Brown. https://archive.org/details/atreatiseonartd00thicgoog/page/n125/mode/2up *Wilkins, John. 1641. Mercury, or The Secret and Swift Messenger. http://lcweb2.loc.gov/cgi-bin/ampage?collId=rbc3&fileName=rbc0001_2009fabyan19070page.db&recNum=168

External links

* Music-based ciphers, online encoders, https://wmich.edu/mus-theo/ciphers * Elgar's Enigma Cipher, https://enigmathemeunmasked.blogspot.com/ * Solfa Cipher, https://solfa-co.de * Music Sheet Cipher, https://www.dcode.fr/music-sheet-cipher {{Authority control Cryptography Ciphers Music theory