Beethoven started going deaf in his late 20s. Already famous by age 25 for his piano sonatas, at 31 he was traumatized by losing his hearing. But he kept on composing: the Moonlight Sonata during the onset of deafness; the dramatic Waldstein Sonata at 32; piano sonatas kept on coming until he was 50. In his deaf period came the revolutionary sounds of his 3rd through 8th symphonies, piano and violin concertos (age 32-40). After 44 he became less productive, with intermittent flashes (Missa Solemnis, Diabelli variations, 9th symphony) composed at 47-53, dying at 56. His last string quartets were composed entirely in his head, left unperformed in his lifetime.
Handel went blind in one eye at age 66; laboriously finished the oratorio he was working on; went completely blind at 68. He never produced another significant work. But he kept on playing organ concertos, "performing from memory, or extemporizing while the players waited for their cue" almost to the day he died, aged 74.
Johann Sebastian Bach fell ill in his 64th year; next year his vision was nearly gone; he died at 65 "after two unsuccessful operations for a cataract." At 62 he was still producing great works; at 64 he finished assembling the pieces of his B Minor Mass (recycling his older works being his modus operandi). At death he left unfinished his monument of musical puzzles, The Art of the Fugue, on which he had been working since 55.
Can we conclude, it is more important for a composer to see than hear?
Beethoven could hear neither music nor conversation; but he spoke to others, reading their words on scribbled notes. Companions described him as humming and howling to himself while walking in the countryside, returning to his piano to work out the fingering-- it was his "Appassionata Sonata". Meeting Carl Maria von Weber, whose revolutionary opera Der Freischutz created a stir, Beethoven embraced him enthusiastically with the words "So you're the very devil of a fellow I've been hearing about!" He could hear the music in his head by reading a score-- like all classical composers, who "auditioned" each other's music from their scores. How else would you know whether to have an orchestra perform it? Hence the importance of seeing: reading a score, envisioning how to write down the music in one's head. It would be near fatal for a composer to be blind.
There are famous blind creators, chiefly in literature.
Milton went blind at age 44; already a notable poet and political controversialist, he went on to compose Paradise Lost (written age 50-55) and Paradise Regained (published at 66, the year of his death).
William H. Prescott was nearly blinded in a college roughhouse; went on to travel seeking original texts from the Spanish conquests of America, listening and writing with the help of amanuenses; publishing The History of the Conquest of Mexico (1843) and Conquest of Peru (1847) when he was 47-51 years old. Without eyesight, he developed a phenomenal memory, and a prose style voluminous and eloquent.
Gibbon wasn't blind, but his method of composing was to form in his head his sonorous rhythmic sentences (his stately "periods" as his contemporaries would say): "cast a long paragraph in a single mould, to try it by my ear, to deposit it in my memory, but to suspend the action of the pen 'til I had given the last polish to my work." [Saunders p.15] In this way he composed the most literary of all histories, the six volumes of Decline and Fall of the Roman Empire (2 million words, written during age 35-50). This comes to some 300 words per day, a do-able process.
Milton and Prescott are similarly stately writers of vivid material, readable even for the sound alone. They are writers whose prose or verse had "music", as the 17th century would put it. Like Beethoven, they could compose in their head. (And by the way, Milton's father was a composer.)
Among blind poets there is famously Homer, although is it thought that "Homer" was the brand-name of a guild of blind reciters; the formulaic epithets for heroic characters and wine-dark seas were memory-hooks for oral performance handed down over the decades.
There is a Japanese equivalent, blind reciters of The Tale of the Heike, the epic samurai history of the twelfth-century wars between the Heike and Genji clans. In the fourteenth century until it was written down in the fifteenth, Heike Monogatari was recited by blind monks wearing Buddhist robes, accompanying themselves on the biwa or lute, called "biwa hoshi" or "biwa monks". Its enormous length (the English translation is 700 pages) was held in memory by poetic/musical forms, in this case the thirty-one syllable waka, ancestral to haiku and other forms, an early hybrid between poetry and prose. [Tyler xxiv]
There are no famous blind painters, to my knowledge; whether painters were deaf no one seems to have regarded as a fact worth noticing. Are there great deaf poets? It has not been bruited about.
My point is not the pathos of difficult lives, nor the triumph of overcoming it. Deaf or blind creators in different fields provide a natural experiment, evidence for what kind of the skill -- including social skill-- is the specific ingredient of creativity in music, and what are specific to other fields.
Music without texts (folk music and the like) is hand-to-ear coordination. With instrument ensembles, it becomes also hand-to-eye coordination.
Playing an instrument is a bodily skill; the whole body may go into the rhythm; the movements of fingers on strings and keys; of arms scraping bows over strings or beating drums; of fingers on stops and valves coordinated with lips and mouth and lungs that is the playing of wind instruments. Opera singers are trained players of their own body cavities and the tensing and relaxing of muscles. All this while keeping an eye on the score, or at least having memorized it. Complex music-- AKA classical music -- is the coordination of instruments and players: a social skill, a social invention. The symphony orchestra was no less an organizational innovation than a factory of workers operating machinery.
Participants in these humans-with-instruments combinations -- composers, players-- practice hand-to-eye-to-ear coordination. When composers are deaf, they can continue to coordinate hand-to-eye and thus generate the social follow-through that is music creation. When composers go blind, they mostly stop composing.
And yet there are a number of blind performer-composers in popular music: Stevie Wonder [blind from birth; Motown contract at 13; his own song albums from 21], Ray Charles [glaucoma as child; studied music at a school for deaf and blind; recorded famous songs in his late 20s], Blind Lemon Jefferson [partially sighted from birth; street singer; gospel and blues recordings in his late 20s]. All were soloists-- singers accompanying themselves on keyboard or guitar; in recordings and performances, sometimes provided with backup musicians and studio directors. All were composers of relatively short songs (3-minutes-plus), in the standard sonata forms of repetitions-and-variations of 20th century popular music. More or less autonomous as performers, they could compose short forms without seeing texts.
Written scores are more central for longer and more elaborately coordinated classical music. In the era before sound recording, composers could only keep up with the music of their peers and rivals-- if they didn't hear it in person-- by circulating their scores. Music publishing coincides with the development of classical music.
Composers were generally performers themselves. Beethoven, who began by improvising dramatically on the piano, continued to perform in his deafness, eventually giving it up, as he gave up orchestra conducting. For him, playing and conducting were bodily habit, that kept for a while its momentum; although he could no longer hear the instruments nor the audience reaction. Handel, who had made his early reputation as the greatest organist and harpsichord player of his time, ended his lengthy stream of operas, oratorios, and concertos when he went blind. That he could continue to play implies that he could rely on memory and muscle skill, but that these alone are not enough to compose new music--- that which enters the repertoire of further musicians by creating written scores.
Music composing, at least in the classical era of large instrumental ensembles, is a cyborg skill. Instruments, performers, composers, all on the same page-- literally.
Writing and reciting, at least for poets and writers of sonorous prose, is a skill of training the inner and outer ear; they create and perform, much less with the eye, combining words on the rhythm of their inner music. (We speak of a writer "finding their voice")
Paradoxically, composers need eyes more than ears; writers need ears more than eyes. But it is no paradox at the level of the blending of inner and social skills that make up what we call creativity.
References
Harvard Biographical Dictionary of Music. 1996.
Chambers Biographical Dictionary. 1986.
Dero Saunders. 1952. Introduction to Edward Gibbon, The Decline and Fall of the Roman Empire.
Royall Tyler. 2012. The Tale of the Heike. Viking Penguin.