歌词解析：
1、I was dancin' with my darlin' to the Tennessee Waltz When an old friend I happened to see
主语+WAS（WERE）+V_ing+WHEN 引导的过去式从句：正在。。。就
DANCE TO +MUSIC 随着音乐起舞
EX： I LOVE THIS SONGVERY MUCH， SHALL WE DANCE TO IT？
2．I was dancing with my darling to the Tennessee waltz.
　　=I was dancing to the Tennessee waltz with my love.
　　我正与心上人随着田纳西华尔兹跳舞
　　to the Tennessee waltz 中的to是“伴随着”的意思。
3．Introduced her to my loved one,…
　　=I introduced her to my darling,…
　　我把她介绍给我的心上人
4．Now I know just how much I have lost．
　　=Now I am fully aware of what a great loss I had.
　　现在方知损失多么惨重。
5．Yes, I lost my little darling the night they were playing the beautiful Tennessee waltz.
　　=Yes, I lost my little darling, at the night when they were playing the beautiful Tennessee waltz.
　　是啊，就在那个晚上伴随着那首动听的田纳西华尔兹我失去了我的爱人
　　the night they were playing…即at the night when they were Playing…，但在习惯用法上，介词at和关系副词when常被省略，因此定冠词加上时间名词可作连接词使用，可称这种情况为合成连词。
　　例：The moment I came, he was reading a book.
　　=When I came, he was reading a book
　　我来时他正在读一本书。
6.When an old friend I happened to see.
　　=（I was waltzing with my darling to the Tennessee waltz） when I happned to see an old friend.
　　happen to:碰巧；恰巧；恰好
　　(和名词连用)临到...头上(某情况, 尤指不幸的事); (和动词连用)偶然; 碰巧
　　例：I happened to be out when she called.
　　她打电话时我碰巧不在家。
　　it happen that:碰巧
　　It happened that I was out when he called.他打电话时我恰巧不在家。