You can think of folk music as a song with no owner. It sits in a village, not on a shelf: someone's grandmother sings it, a child hears it and sings it later, and nobody ever asks who wrote it. Everything else the words mean grows out of that picture — including the modern style, which is new music made to sound like it came from that village.
folk + music, where folk is the ordinary people of a place.
folk（一般人、老百姓）加上 music（音樂）：字面上就是「老百姓的音樂」。這是從詞本身拆解出來的，不是引用歷史語源考證。
transparent compound of the English words folk + music; no cited etymology supplied in the evidence packet
One branch
老百姓的歌
兩個意思都扣著同一幅畫面，差別只在一個是真的從村子傳下來的，另一個是做出來像村子的聲音。
noun · B1
Music that ordinary people in one place have sung and played for a very long time. Nobody owns it, and it is usually learned by ear from older singers rather than from written music.
民謠／民俗音樂
以下是外部詞典記錄的用法，原文照列，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
folk musicnoun
Any genre of music originating from the ethnic community of a specific region, often passed down through oral tradition, without recorded songwriters and possessing a clear purpose or social function.
Any contemporary music in the style of traditional folk music, especially a specific genre of originally American popular music that draws on Anglo-American musical forms.
資料來源：英文維基詞典 English Wiktionary（CC BY-SA 4.0）。 原文照列，未經改寫。