Which composer wrote his Ninth Symphony while almost completely deaf?

Answer

He premiered it in 1824 and famously had to be turned around to see the applause.

Context

Beethoven's hearing declined from his late twenties, and by the time of the Ninth Symphony he was almost entirely deaf, relying on written conversation books and his musical imagination. Britannica notes that deafness made him more of a recluse than ever and slowed his composing in his final period. The Ninth was his last work for large-scale forces.

The premiere took place in 1824 at the Kärntnertor Theatre in Vienna on a programme that also included movements of the Missa Solemnis and the overture Op. 124. Britannica records that he remained unaware of the applause until one of the soloists turned him to face the audience. A professional conductor handled the actual direction while Beethoven took part on stage, according to the usual account.

The symphony ends with a choral finale on Schiller's poem An die Freude, now called the Ode to Joy, which is generally regarded as the first time a major composer put voices into a symphony. The London Philharmonic Society had a hand in prompting the work, in a sense commissioning it, and the printed edition carried a dedication to Frederick William III of Prussia.

Composing without hearing was less contradictory than it sounds. Beethoven had decades of trained inner hearing, and sketchbooks show him working out ideas on paper in detail; the symphony came out of that process, not out of live listening.