ontei ga atte iru.

It is read おんてい が あって いる.

In normal Japanese writing, you would usually see it written without spaces:

音程が合っている。

The spaces here are just a learner-friendly way to show the parts of the sentence more clearly.

• 音程 = おんてい
• が = subject marker
• 合っている = あっている

音程 literally refers to musical pitch relationship or interval.

But in everyday comments about singing or playing music, it often works like pitch in English. So when someone says 音程が合っている, they usually mean the notes are correct and the person is in tune.

So the word is musical in nature. It is not the usual word for ordinary pronunciation problems in speech.

が marks 音程 as the thing being described.

In other words, the sentence is saying that the pitch is what matches / is correct.

A very literal breakdown is:

• 音程 = pitch
• が = subject marker
• 合っている = is matching / is in a matched state

So the grammar is basically: The pitch is matched / in tune.

If you used は instead, the nuance would change. For example, 音程は合っている could sound more like as for the pitch, it is correct, possibly with contrast implied.

It comes from the verb 合う.

Here, 合う means things like:

• to match
• to fit
• to be correct
• to be in sync

So:

• dictionary form: 合う
• て-form: 合って
• ている form: 合っている

Be careful: あう can represent different verbs in Japanese.

• 合う = to match, fit, suit
• 会う = to meet someone

Here it is definitely 合う, not 会う.

Here, ている is mostly showing a current state, not an action actively happening in front of you.

So 音程が合っている does not mainly mean the pitch is currently in the process of matching. It means more like:

• the pitch is matched
• the pitch is correct
• the person is in tune

This is a very common use of ている in Japanese. It often describes the result or current state produced by a verb.

So in this sentence, 合っている is best understood as a state: the pitch is in the right place.

Yes, you can, but the nuance is a little different.

音程が合う is the plain non-past form and can mean things like:

• the pitch matches
• the pitch will match
• the pitch tends to be correct

音程が合っている focuses more clearly on the present state of being in tune.

Very roughly:

• 音程が合う = the pitch matches
• 音程が合っている = the pitch is matched / is in tune right now

In actual conversation, both can be natural depending on context.

That is very normal in Japanese.

Japanese often leaves out information that is already clear from context. So 音程が合っている could mean:

• your pitch is in tune
• his pitch is in tune
• her singing is in tune
• this singer is in tune
• the instrument is in tune

The listener is expected to figure that out from the situation.

If you want to state it explicitly, you could say things like:

• 彼は音程が合っている。 = He is in tune.
• この歌手は音程が合っている。 = This singer is in tune.

It is a complete and natural sentence in Japanese, especially in conversation.

Even though English usually wants an explicit subject like she, he, or the singer, Japanese often does not need one if the context already makes it obvious.

So a short sentence like 音程が合っている。 sounds perfectly normal as a comment such as:

• about someone singing
• about a performance
• about a recording
• about an instrument

Yes. It can be used for both.

For example, it can describe:

• a singer hitting the correct notes
• a violin or guitar being in tune
• a performance where the notes are correct

However, for ordinary spoken language, Japanese usually uses different words. If you are talking about how someone speaks, words like these are more common:

• 発音 = pronunciation
• イントネーション = intonation
• アクセント = accent/pitch accent

So 音程が合っている sounds musical rather than about everyday speech.

A polite version is:

音程が合っています。

A negative version is:

音程が合っていない。
or politely:
音程が合っていません。

You may also hear:

音程が合わない。

This is also very natural and often means the pitch does not match / is off.

So some useful forms are:

• 音程が合っている。 = The pitch is in tune.
• 音程が合っています。 = polite
• 音程が合っていない。 = The pitch is not in tune.
• 音程が合っていません。 = polite negative
• 音程が合わない。 = The pitch does not match / is off

Yes.

音程が合っている is specifically about pitch accuracy. It means the notes are correct.

But being a good singer involves more than that, such as:

• rhythm
• tone quality
• expression
• breath control
• style

So if you say 音程が合っている, you are praising one specific aspect: their pitch is accurate. It does not automatically mean they are an excellent singer overall.