Why is it easy to sing along with pop songs?

Why is it easy to sing along with pop songs?
Because the same melody is repeated over and over again.
"Hey Jude" is a perfect example of the most popular songs.

為什麼流行歌曲容易朗朗上口？ 因為旋律持續重複。
來聽聽一個很棒的例子： Hey Jude

演唱：披頭四樂隊

In classical music, we can recognize Ravel's Bolero easily because it's consisted of the same rhythm and melody being repeated over and over again. Maurice Ravel (French, 1875 – 1937) composed this piece in the early 20th century. Let’s listen to it.

古典音樂中，法國作曲家拉威爾(1875 – 1937)在20世紀初創作的西班牙舞曲：波麗露 (又稱為：博萊羅)，也出現旋律和節奏持續重複的情況，一起來聽聽。