song, sing

歌 is composed of 哥 (elder brother) and 欠 (owe). 哥 conveys the idea of multiple elders sounding together, while 欠 depicts a person opening their mouth to exhale. The original meaning of 哥 is the sound produced in harmony with a musical melody. Later, as 哥 developed other meanings, the character 歌 was separately created to express that original sense.