Lời bài hát khó đến nỗi tôi muốn đọc lại.

Lời bài hát means the lyrics of a song or song lyrics.

It breaks down like this:

• lời = words, wording, lyrics
• bài hát = song

So lời bài hát is literally something like the words of the song.

A useful thing to notice is that Vietnamese often links nouns without using of or 's:

• lời bài hát = lyrics of the song
• tên bài hát = name of the song
• ca sĩ nổi tiếng = famous singer

In this sentence, lời bài hát is the subject.

Because Vietnamese often does not use a copula like to be before adjectives.

So:

• Lời bài hát khó = The lyrics are difficult
• Bài hát hay = The song is good
• Cô ấy đẹp = She is beautiful

In Vietnamese, an adjective like khó can directly describe the subject without needing a separate word meaning are.

Đến nỗi means so ... that ... or to the point that ....

The pattern is:

• [adjective/verb] + đến nỗi + [result clause]

So in this sentence:

• khó đến nỗi tôi muốn đọc lại
• so difficult that I want to read it again

It introduces the result or consequence of something being very intense.

More examples:

• Mệt đến nỗi tôi ngủ ngay.
  So tired that I fell asleep immediately.

• Đẹp đến nỗi ai cũng nhìn.
  So beautiful that everyone looked.

Not exactly.

• quá khó = too difficult / very difficult
• khó đến nỗi... = so difficult that...

The difference is that đến nỗi usually leads to a result.

Compare:

• Lời bài hát quá khó.
  The lyrics are too difficult / very difficult.

• Lời bài hát khó đến nỗi tôi muốn đọc lại.
  The lyrics are so difficult that I want to read them again.

So đến nỗi does more than just intensify; it connects the difficulty to what happens next.

Here, lại means again, so đọc lại means read again or reread.

In Vietnamese, lại often comes after the verb when it means repetition:

• xem lại = watch again / review
• nghe lại = listen again
• đọc lại = read again
• làm lại = do again

So đọc lại is the normal, natural order.

You may also see lại before a verb in other situations, but that often creates a different emphasis or structure. For simple do it again meaning, verb + lại is the safest pattern.

Usually it just means read again. Whether it is silent reading or reading aloud depends on context.

Since the sentence is about lyrics, đọc lại most naturally means reread the lyrics on a page or screen.

If you specifically wanted listen again, you would say:

• nghe lại = listen again

For example:

• Lời bài hát khó đến nỗi tôi muốn nghe lại.
  This would suggest listening again, not rereading.

Tôi muốn đọc lại is understandable and natural enough if the idea is:

• The lyrics are so difficult that I feel like reading them again
• The lyrics are so difficult that I want to go over them again

But many learners notice that with difficulty, phải can sound more logical:

• tôi phải đọc lại = I have to read again
• tôi cần đọc lại = I need to read again

So the nuance is:

• muốn = want to
• cần = need to
• phải = have to / must

All are possible, but they are not identical.

Yes, you could.

• lời bài hát = common, everyday way to say song lyrics
• ca từ = more literary, formal, or stylistic

So:

• Lời bài hát khó đến nỗi tôi muốn đọc lại.
• Ca từ khó đến nỗi tôi muốn đọc lại.

Both are possible, but lời bài hát is usually the more straightforward choice for learners.

Vietnamese does not have articles like the or a/an in the same way English does.

So lời bài hát can mean:

• the lyrics of the song
• song lyrics

The exact meaning depends on context.

In real use, if everyone already knows which song is being discussed, English often translates it with the:

• Lời bài hát khó...
  The lyrics are difficult...

But Vietnamese itself does not need a separate word for the here.

Yes. This is a very useful pattern:

• [subject] + [adjective/verb] + đến nỗi + [result]

Examples:

• Bài này khó đến nỗi tôi không hiểu.
  This lesson is so difficult that I don’t understand it.

• Cô ấy đẹp đến nỗi ai cũng nhìn.
  She is so beautiful that everyone looks at her.

• Anh ấy mệt đến nỗi không nói được.
  He is so tired that he can’t speak.

So your sentence is a good model for learning a broader grammar pattern.