Several parts combine into one character.

音 is a brilliantly minimal differentiation: take 言 (speech / word) and add one extra horizontal stroke inside the mouth (口). That single added line represents "speech without meaning — pure sound." The character itself documents an ancient conceptual leap: language and sound are not the same thing, and need separate words. This kind of philosophically aware character formation is rare in any writing system. The 音 radical anchors a family of auditory and emotional characters: 韻 (yùn, rhyme), 響 (xiǎng, to resound), 暗 (àn, dark — "without sound"), 闇 (dim).

Korean reading "eum." 音樂 (eumak, music), 音聲 (eumseong, voice / sound), 發音 (bareum, pronunciation), 和音 (hwaeum, harmony / chord), 騷音 (soeum, noise). Crucially, the very framework of Sino-Korean kanji learning is built on this character: the famous "字 + 音 + 訓" (character + sound + meaning) trinity makes 音 itself the meta-vocabulary of pronunciation.

Mandarin yīn, 1st tone. 音乐 (yīnyuè, music), 声音 (shēngyīn, sound — note 声 also means sound, doubling for clarity), 发音 (fāyīn, pronunciation), and 拼音 (pīnyīn, the Romanization system for Chinese — literally "spelled-together sounds"). The very name of the global standard for transcribing Chinese sounds embeds this character. 噪音 (zàoyīn) = noise, 录音 (lùyīn) = audio recording.

Japanese has two on-readings reflecting different historical borrowings. オン (on) — 音楽 (ongaku, music), 音声 (onsei, voice), 発音 (hatsuon, pronunciation). イン (in) — 母音 (boin, vowel / "mother-sound"), 子音 (shiin, consonant / "child-sound"). The two kun-readings are emotionally distinct: おと (oto) = objective, neutral sound (足音 ashioto, footsteps); ね (ne) = sound carrying mood, atmosphere, or aesthetic feeling — particularly used in 虫の音 (mushi no ne, the song of insects) and 鐘の音 (kane no ne, the resonance of a bell). The おと/ね split is one of the most subtle and beautiful semantic distinctions in spoken Japanese.

Memory aid: speech (言) with one extra line inside the mouth — sound divorced from meaning.