音樂裡的和聲
這一組就是核心畫面本身，沒有比喻成分：真的有幾條不同的音疊在一起。
verb · B2
To sing or play notes that are not the main tune but sound good with it, so that the voices or instruments together make one fuller sound.
和聲、合聲
核心畫面
You can think of harmonize as two voices singing notes that are not the same. One carries the tune; the other sits above or below it. They stay different, yet the two lines lean on each other and come out as one rounder sound. Every other use of the word can be read off that picture: keep the parts different, choose them so they fit, and the whole thing stops sounding like noise.
harmonize 的核心畫面可以想成兩個人一起唱歌。一個唱主旋律，另一個唱不一樣的音。兩條線始終沒有變成同一條，可…更多收起
harmonize 的核心畫面可以想成兩個人一起唱歌。一個唱主旋律，另一個唱不一樣的音。兩條線始終沒有變成同一條，可是疊在一起卻更飽滿、更好聽。這個畫面裡有兩件事同時成立：保持不一樣，而且彼此合得來。後面所有的用法，都可以當成從這個畫面長出來的——把「音」換成房子的顏色、換成各國的稅率，道理一樣。From the word’s history
Wiktionary gives harmonize as from French harmoniser, and by surface analysis harmony + -ize, that is, to make things into harmony. The musical sense sits closest to that literal build.
Wiktionary 記載 harmonize 來自法文 harmoniser，就字面拆解則是 harmony（和聲、和諧）加上 -ize（使變成…），也就是「使之成為和諧」。音樂上的用法最貼近這個字面結構，其他用法讀起來像是從這裡借出去的。
Wiktionary entry for harmonize (packet etymology_text): From French harmoniser. By surface analysis, harmony + -ize.
Three branches
東西之間合得來
把「音」換成顏色、形狀、氣味或做事方式：東西還是各自不同，但放在一起不刺眼，就像兩個聲部不打架。
verb · B2
If two or more things harmonize, they go well together, so nothing clashes. The parts stay different, but they fit each other and the whole thing looks or feels right.
協調／相襯
把規則調成一致
各地各有各的規定，就像每個人各唱各的；把它們調到同一套，才不會互相卡住。這一組跟前兩組有個差別：這裡真的要求「變成一樣」，不只是合得來。
verb · C1
To change two or more sets of rules, taxes, standards or systems so that they become the same, or close enough to work together, across different countries, companies or departments.
使一致、統一標準