ane ha oozei no mae de utauno wo hazukasigaru keredo, hitori de ha yoku utatte iru.

姉は marks older sister as the topic of the sentence.

So the sentence is talking about the older sister, and everything after that describes her behavior.

• 姉は = As for my older sister...
• It does not necessarily mean she is the grammatical subject in the same way as English; it marks what the sentence is about.

Also, in Japanese, 姉 usually means my older sister when speaking to someone outside the family.

大勢 means a large number of people / many people.

前 means front, and 〜の前で means in front of ~.

So:

• 大勢の前で = in front of many people
• more literally: before a large crowd

The particle で marks the setting or situation where the action happens.

Because 歌う is a verb, and Japanese usually cannot attach を directly to a plain verb that way. The verb has to be turned into a noun-like phrase first.

That is what の is doing here.

• 歌う = to sing
• 歌うの = singing / the act of singing
• 歌うのを = marks singing as the thing connected to the next verb

So 歌うのを恥ずかしがる means something like:

• to be shy/embarrassed about singing
• literally, to feel embarrassed about the act of singing

Yes, 歌うことを is grammatically possible in many cases, but 歌うのを sounds more natural here.

A useful guideline:

• の often feels more direct, concrete, or tied to an actual action
• こと can sound more abstract or formal

Since this sentence is about the very real activity of singing in front of people, 歌うのを恥ずかしがる is a natural choice.

This is an important point.

• 恥ずかしい = to feel embarrassed / ashamed
• 恥ずかしがる = to show embarrassment / to act shy / to be shy about something

Why use 恥ずかしがる here?

In Japanese, when talking about another person's internal feelings, it is often more natural to use a form like 〜がる, which describes the way they appear or behave, rather than directly stating their feelings.

So:

• 姉は歌うのを恥ずかしがる = My older sister is shy about singing
• It focuses on her observable behavior or tendency

This is more natural than directly saying 姉は恥ずかしい in this context.

Because を here marks the thing that she feels shy or embarrassed about.

In Japanese, some emotional or attitude-related expressions can take an object-like phrase with を.

So in:

• 歌うのを恥ずかしがる

the meaning is:

• to be shy about singing
• to feel embarrassed about singing

It is not that she does the singing as the object of 恥ずかしがる. Rather, singing is the thing that triggers the embarrassed feeling.

けれど means but / although / however.

It connects two contrasting ideas:

• she is shy about singing in front of many people,
• but she sings a lot when she is alone.

So it shows a contrast between:

• public singing → shy
• singing alone → does it often

In conversation, けれど often sounds a little softer than a blunt but in English.

Because the は adds contrast.

• 一人で = alone / by herself
• 一人では = when she is alone, on the other hand...

So the sentence contrasts two situations:

• 大勢の前で = in front of many people
• 一人では = when alone, by contrast

This は is not the main topic marker here. It is a contrastive は.

Here, よく means often.

So:

• よく歌っている = she often sings

Be careful: よく can also mean well, depending on context.

For example:

• よく歌う = sing often
• 歌がよく歌える or context-dependent uses could suggest sing well

In this sentence, because of the contrast with being shy in public, often is the natural meaning.

Both can refer to repeated actions, but 歌っている gives a sense of an ongoing habit or a state that is regularly observed.

So:

• 一人ではよく歌う = she often sings when alone
• 一人ではよく歌っている = when she is alone, she is often singing

The 〜ている form here suggests a habitual, commonly seen pattern rather than a simple plain statement.

It can feel a little more vivid, as if describing what she is like in real life.

姉 by itself means older sister, but whose older sister it refers to depends on context.

Commonly:

• 姉 = my older sister when talking about your own family to others
• お姉さん = someone else’s older sister, or a polite/friendly way to say older sister / young woman

So in this sentence, 姉 most naturally means my older sister.

It breaks down like this:

• 姉は — as for my older sister,
• 大勢の前で — in front of many people,
• 歌うのを — singing / the act of singing,
• 恥ずかしがる — she is shy about it,
• けれど — but,
• 一人では — when alone, by contrast,
• よく歌っている — she often sings

So the sentence has two main parts joined by けれど:

1. She is shy about singing in front of many people
2. But when she is alone, she often sings