音 grew from the same early family as 言, “speech”. Ancient forms add a mark in or near the mouth-like lower part, distinguishing the audible sound or tone from words in general. The exact appearance changed across bronze and seal scripts, but the relationship between speech and heard sound remained. This ancient-form-inspired sketch therefore echoes 言 while placing clear sound marks inside its lower box.
A piece of culture
Hear the tone, hear the meaning Mandarin and Cantonese are tonal: the pitch pattern of a syllable helps distinguish one word from another. 音 appears in useful learning words such as 发音 / 發音, “pronunciation”, and in 音乐 / 音樂, “music”. Pinyin tone marks and Jyutping tone numbers are therefore not decoration; they record part of the spoken word.