1. You want to find a good song to dance to.

dance to按......节拍跳舞，伴随......跳舞

其中to为介词，按......节拍；伴随......

The type of music has become very famous in Britain and is very good music to dance to.

这种音乐在不列颠很著名，是很好的伴舞的音乐。

She often sings to the piano.

她常用钢琴伴唱。

2. There is a world of music out there!

a world of无数......；大量......；许多......

The praise did me a world of good.

那表扬对我大有好处。

It makes a world of difference whether precautions are taken or not.

有没有预防措施是大不一样的。

3. The blues comes from African songs that people used to sing when they worked and during festivals.

used to do（以前）常做；（过去）习惯做

used to的否定形式 usedn't to或didn't use to，疑问形式则写成：Did... use to或Used... to...?

used to后接不定式，表示"过去常做某事"，多表示与现在的对比，暗示"现在不做"。

would表示过去"习惯性或经常性动作"，不与现在对比。

He didn't use to drink. / He usedn't to drink.

他以前不习惯喝酒。

He would go to see mother every vacation.

他每个假期都去看妈妈。

used to和be used to

used to后跟不定式表示"过去常做某事"，用于过去时，be used to后跟名词和动名词，表示"习惯于"某一客观事实和状态。

You'll soon get used to the weather here.

In the end I got used to doing hard work.

最后我终于习惯干苦活了。