also: ぎょくいん
noun
the Emperor's voice
Specifically refers to the voice of the Emperor of Japan, often used in historical or formal contexts, especially regarding the 1945 radio broadcast of the surrender.
終戦の日、国民は初めて玉音放送を聞いた。
On the day the war ended, the people heard the Emperor's voice broadcast for the first time.
noun
Literary or poetic term for a voice or sound that is as beautiful as a gem. Not used in everyday conversation.
彼女の歌声はまさに玉音と称するにふさわしい。
Her singing voice is truly worthy of being called a beautiful sound.
The specific historical broadcast of the Emperor's surrender speech in 1945; 玉音 alone refers to the voice itself.
From 玉 (jewel, beautiful) + 音 (sound, voice). The exact historical derivation is uncertain, but the term has been used in classical Chinese and Japanese to refer to an emperor's voice or a beautiful sound.