utagoe ga kirei da.

歌声 is read うたごえ.

It is made from:

• 歌 = song, singing
• 声 = voice

So 歌声 means singing voice or voice while singing.

They are related, but not the same:

• 歌 = a song, or singing
• 声 = voice
• 歌声 = singing voice

So 歌声がきれいだ means the voice itself is beautiful when singing, not necessarily that the song is beautiful.

For example:

• 歌がきれいだ would sound odd in most situations, because songs are usually described with words more like いい, すてき, or 美しい
• 声がきれいだ means the voice is beautiful
• 歌声がきれいだ specifically focuses on the person’s singing voice

In 歌声がきれいだ, が marks 歌声 as the thing being described.

So the structure is basically:

• 歌声 = singing voice
• が = marks what is being talked about as the subject of the description
• きれいだ = is beautiful / is pretty / is clean, depending on context

Here, が tells you that the singing voice is what is beautiful.

A very natural translation is:

• The singing voice is beautiful.

Both are possible, but they give a slightly different feel.

• 歌声がきれいだ = focuses on the fact that the singing voice is beautiful
• 歌声はきれいだ = as for the singing voice, it is beautiful

A simple way to think about it:

• が often presents or identifies the thing with the quality
• は marks the topic and can sound more contrastive or more like a general statement about that topic

So:

• 歌声がきれいだ can sound more like What is beautiful? The singing voice is.
• 歌声はきれいだ can sound more like As for the singing voice, it is beautiful—possibly implying comparison with something else

In isolation, が is very natural here.

No. きれい is not an -i adjective. It is a na-adjective.

This is a very common point of confusion, because it ends in い. But grammatically, it behaves like a na-adjective:

• きれいだ = is beautiful / is clean
• きれいな声 = a beautiful voice
• きれいではない = is not beautiful / is not clean

So in this sentence, きれいだ is the correct plain form.

The だ is the plain-form copula. It makes the sentence complete.

So:

• 歌声がきれいだ = plain style
• 歌声がきれいです = polite style

You can think of だ here as the plain-style equivalent of です.

In casual conversation, Japanese sometimes drops だ, especially in certain contexts, so you may also hear:

• 歌声がきれい

But in textbook-style grammar, きれいだ is the full plain form.

Here it means beautiful or pretty.

きれい can mean both:

• clean
• beautiful / pretty

The context tells you which meaning is intended.

With 歌声 meaning singing voice, the natural meaning is clearly:

• beautiful
• lovely
• pretty

A clean singing voice would not usually be the first interpretation unless the context strongly suggested something technical about sound.

Japanese often leaves out information that is understood from context.

So 歌声がきれいだ by itself just says:

• The singing voice is beautiful.

In real conversation, the listener usually already knows whose singing voice is being discussed.

For example, it could mean:

• Her singing voice is beautiful.
• Your singing voice is beautiful.
• That singer’s singing voice is beautiful.

If you want to say it explicitly, you can add it:

• 彼女の歌声がきれいだ = Her singing voice is beautiful
• あなたの歌声はきれいです = Your singing voice is beautiful

Not exactly.

歌声がきれいだ describes the voice, not the action of singing.

So it is closer to:

• The singing voice is beautiful
• He/She has a beautiful singing voice

If you want to say someone sings beautifully, Japanese would more naturally use a verb or adverb, such as:

• 歌い方がきれいだ = the way of singing is beautiful
• きれいに歌う = sing beautifully

So 歌声がきれいだ focuses on the quality of the voice itself.

The polite version is:

• 歌声がきれいです。

That is the most straightforward polite equivalent.

Compare:

• 歌声がきれいだ。 = plain
• 歌声がきれいです。 = polite

Both mean the same thing. The difference is just speech level.

Because きれい is a na-adjective, you use な before a noun.

So:

• きれいな歌声 = a beautiful singing voice

This matches the sentence:

• 歌声がきれいだ = The singing voice is beautiful

These are related patterns:

• Noun + が + きれいだ
• きれいな + Noun

For example:

• 歌声がきれいだ = The singing voice is beautiful
• きれいな歌声だ = It is a beautiful singing voice

Since きれい is a na-adjective, its forms work like this:

Plain forms:

• 歌声がきれいだ = The singing voice is beautiful
• 歌声がきれいではない = The singing voice is not beautiful
• 歌声がきれいだった = The singing voice was beautiful
• 歌声がきれいではなかった = The singing voice was not beautiful

Polite forms:

• 歌声がきれいです
• 歌声がきれいではありません
• 歌声がきれいでした
• 歌声がきれいではありませんでした

This is useful because きれい does not conjugate like a true -i adjective such as 高い.