Some interesting metaphorical history here.
For the Record: Adorno on Music in the Age of Its Technological Reproducibility
Thomas Y. Levin
October, Vol. 55. (Winter, 1990), pp. 23-47.
. . . particularly on pp. 35-38, where Esperanto is discussed. See the original text for illustrations.
At first glance there is a striking similarity between Adorno's evocation of a post-lapsarian utopia and the universal language topos that accompanied early cinema.  The parallel logic in what one could call the Esperantist conception of the cinema is evident, for example, in D. W. Griffith's claim in a 1921 interview that "A picture is the universal symbol, and a picture that moves is a universal language. Moving pictures, someone suggests, 'might have saved the situation when the Tower of Babel was built.' "  Just as cinema was heralded as a transparent, unproblematically accessible (because visual) alternative to national languages, an analogous discourse of democratization and univocal, natural signs accompanied the prehistory and invention of the phonograph. During the first half of the nineteenth century, phonography—defined in the OED as "a system of phonetic shorthand invented by Isaac Pitman in 1837"—was heralded as a "natural method of writing"  and was arduously defended by worker's groups as a means of making writing more widely accessible.  In the same vein, the "phonautographe," invented by Léon Scott de Martinville in 1857, was an attempt to produce, as the machine's subtitle explained, an "Apparatus for the Self-Registering of the Vibrations of Sound." The resulting "natural stenography" would be, according to the title of Scott's book on the subject, sound writing itself.  Illiteracy would thus be eliminated by substituting hearing and speaking for reading and writing. Indeed, one of the most popular uses of the early phonographs—which, one should recall, could both play and record—was acoustic correspondence. The "phono-post" speaking postcards, which one recorded and sent through the mails, made writing superfluous, a fact stressed by advertisements that invited potential users to drop their dictionaries and "Speak! Don't write any more! Listen!"OK, most of this will be impenetrable gobbledegook to most of you, though it fits in to my research interests. But note that the universal language idea became popular for the first time in the 19th century, and as a master metaphor persisted into the early 20th century. The popular universal interest in a universal language dovetails with various media, symbolic codes, notations, etc. that could function as "universal languages". Of course, people still use the word "Esperanto" neutrally, positively, or pejoratively in a metaphorical sense, but we're in a different era. I wonder if it was the 1930s that killed off this earlier sensibility, both metaphorically as well as literally.
Unlike the visual Esperanto of the cinema, however, the possibility of universal language held out by the gramophone is just that: only a possibility, a hope. While the traces of the gramophone are just as indexical as the cinematic signifiers, they are not, as Adorno is careful to point out, readily intelligible like photographs. Rather, they are both indexical and enigmatic. In this regard they can claim both of the contradictory qualities of the hieroglyph: "universal" and "immediate" by virtue of their "natural," necessary relation of sign to referent, and also esoteric, recondite and requiring decoding, due to their surface inaccessibility.  Phonograph records are, to quote an astonishing early anticipation of Adorno's techno-cryptogrammic characterization, "cabalistic photographs [by means of which] sound can outlive itself, leave a posthumous trace, but in the form of hieroglyphs which not everyone can decipher."  Despite their shared millenarian formulations, the universal language rhetoric accompanying early cinema is thus far indeed from the post-Babelian figure employed by Adorno in his recuperation of gramophonic reification by means of what is almost a theology of indexicality. The latter must be located, rather, in a very different tradition: the hieroglyphics of nature articulated in German romanticism and, in particular, as mediated by Walter Benjamin.
27. As Miriam Hansen has pointed out, this metaphor of universal language, which was "used by journalists, intellectuals, social workers, clergy, producers, and industrial apologists alike . . . drew on a variety of discourses (Enlightenment, nineteenth-century positivism, Protestant millennialism, the Esperanto movement, and the growing advertising industry) and oscillated accordingly between utopian and totalitarian impulses" (Miriam Hansen, "The Hieroglyph and the Whore: D. W. Griffith's Intolerance," The South Atlantic Quarterly 88 (Spring 1989), p. 362. For more on the universal language discourse in early cinema, see also Hansen's "Universal Language and Democratic Culture: Myths of Origin in Early American Cinema," in Myth and Enlightenment in American Literature: In Honor of Hans-joachim Lang, ed. Dieter Meindl, et al. (Erlangen: Universitätsbund Erlagen-Nürenberg, 1985), pp. 321 -51.
28. D. W. Griffith, "Innovations and Expectations," in Focus on Griffith, ed. Harry M. Geduld (Englewood Cliffs, N.J.: Prentice-Hall, 1971), p. 56.
29. See Pitman's 1840 treatise, Phonography; or, Writing by Sound; Being a Natural Method of Writing, Applicable to all Languages, and a Complete System of Shorthand (London: S. Bagster & Sons, 1840).
30. This accounts for its appearance as a topic of debate at the 1867 congress of the International Worker's Association in Lausanne, a discussion that is summarized in G. Duveau, La Pensée ouvrière sur l'éducation pendant la Révolution et le Second Empire (Paris: Domat-Montchrestien, 1947), pp.115- 16.
31. Edouard-Leon Scott de Martinville, Le Problème de la parole s'écrivant elle-même: La France, l'Amérique (Paris, 1878). Earlier Scott had published a study of stenography entitled Histoire de la Sténographie depuis les temps anciens jusgu'à nos jours (Paris: Ch. Tondeur, 1849).
32. As an early nineteenth-century scholar has pointed out, ancient hieroglyphs were also, in fact, phonographic: "Hieroglyphic characters are either ideographs, that is, representations of ideas, or phonographs, that is, representationsof sounds" (Hincks, On Hieroglyphics, cited in OED
33. Emile Gautier, Le Phonographe: son passé, son présent, son avenir (Paris: Ernest Flammarion, 1905), p. 28. The implication in Gautier's remark that some people might be able to "read" the gramophone record is curiously confirmed by the case of Tim Wilson, a thirty-three-year-old Englishman who made the rounds of British and American talk shows in 1985 demonstrating his particular ability to identify unlabeled records, ostensibly by reading the patterns of the grooves (DPA press release, October 1985).