Several parts combine into one character.

歌 is a phonetic-semantic compound built from two halves: 哥 (gē, originally a doubled 可+可 meaning "to make sound repeatedly") on the left provides the sound, and 欠 (qiàn, a side-view of a person with mouth open in exhalation) on the right provides the action. The composite picture is concrete: a person opens the mouth wide and lets sustained, melodic sound flow out — that is singing. The 欠 radical generates a small but emotionally vivid family of "what the open mouth produces" characters: 歡 (joy / loud delight), 歎 (sigh / lament), 飲 (drink — taking in through the open mouth).

Korean reading "ga." 歌手 (gasu, singer), 歌詞 (gasa, lyrics), 國歌 (gukga, national anthem), 愛國歌 (aegukga, "Patriotic Song" — the official name of the South Korean national anthem), 校歌 (gyoga, school song), 詩歌 (siga, poetry / verse). 歌 is the dominant character for "song" in formal Korean compounds, while (norae) is the native everyday word.

Mandarin gē, 1st tone. 歌 (gē, song), 歌曲 (gēqǔ, song / musical piece), 歌手 (gēshǒu, "song-hand" = singer), 唱歌 (chànggē, to sing — literally "perform-song"), 国歌 (guógē, national anthem), 流行歌 (liúxínggē, pop song). The compound 唱歌 (changga) entered Korean as 창가 — preserved as a historical genre label for early modern Korean songs, especially educational and patriotic songs of the early 20th century.

Japanese on-reading カ (ka) — 歌手 (kashu, singer), 校歌 (kōka, school song), 国歌 (kokka, national anthem), 詩歌 (shīka or shiika, poetry). Kun-reading うた (uta) is the everyday Japanese word: 歌 (uta, song), 歌う (utau, to sing), 歌声 (utagoe, singing voice). Japan's native poetic forms preserve uta in their names: 短歌 (tanka, "short poem" — a 5-7-5-7-7 syllable form, the classical mainstream of Japanese poetry), 和歌 (waka, "Japanese poetry" — a broader term encompassing tanka and other native verse forms). Each of these Japanese poetic traditions treats the poem as inherently musical — verse and song share the same word.

Memory aid: 哥 (sound + sound) plus 欠 (open mouth) — making sustained sound through an open mouth is singing.