sing along 中的 along 意思“随同”“一起”的意思，根据《牛津短语动词词典》短语词典：后接某人时用 sing alongwith；后接某事物时用 singalong with / to。该词典对该短语的解释为 tosing together with sb who is already singing or while a record, radio, ormusical instrument is playing 随着（某人、唱片等）唱。如：

1. If you know the words, sing along with us. 如果你知道歌词，请跟我们一起唱。（《韦氏高阶英语词典》）

2. He sang along with the CD. 他跟着光盘唱歌。（《牛津短语动词词典》）

3. We listen to children's shows on the radio, and Janey can sing along with all the tunes. 我们收听收音机上的儿童节目，珍妮能跟着唱所有的曲子。(《柯林斯Cobuild高阶英汉双解学习词典》)

4. We sang along to all the songs. 我们跟唱了所有的歌。（《牛津短语动词词典》）

5. You can sing along to your favourite Elvis hits. 你可以跟着一起唱你最喜爱的“猫王”的热门歌曲。(《柯林斯Cobuild高阶英汉双解学习词典》)