deetto wo utaou.

を marks the direct object of the verb. Here, the verb is 歌おう, from 歌う meaning to sing, so デュエット is the thing being sung.

So the structure is:

• デュエット = duet
• を = object marker
• 歌おう = let’s sing / I’ll sing

This is very similar to sentences like:

• 歌を歌う = to sing a song
• 国歌を歌う = to sing the national anthem

Even though duet is a type of performance, Japanese treats it as the object of 歌う here.

歌おう is the volitional form of 歌う.

• dictionary form: 歌う
• volitional form: 歌おう

The volitional form often means:

• let’s sing when inviting someone
• I’ll sing when expressing one’s own intention

In a sentence like デュエットを歌おう, the most natural interpretation is usually Let’s sing a duet.

歌う is a u-verb. For u-verbs, the volitional form is made by changing the final -u sound to the -ō form.

So:

• 歌う
• final う changes to おう
• result: 歌おう

More examples:

• 行く → 行こう = let’s go
• 読む → 読もう = let’s read
• 話す → 話そう = let’s talk

So 歌う → 歌おう follows a very common pattern.

They are similar, but not exactly the same in tone.

• 歌おう = plain/casual volitional
• 歌いましょう = polite invitation/suggestion

So:

• デュエットを歌おう。 sounds casual, friendly, direct
• デュエットを歌いましょう。 sounds more polite or formal

You might use 歌おう with friends, family, or in song lyrics.
You might use 歌いましょう in class, with strangers, or in more polite situations.

Grammatically, the volitional form can mean either:

• Let’s sing a duet
• I’ll sing a duet

But in this sentence, without extra context, learners will most often understand it as Let’s sing a duet.

Why? Because using the volitional with an action like this often sounds like a suggestion or invitation when spoken to someone.

If the speaker clearly means only their own intention, context usually makes that obvious.

デュエット is a loanword, borrowed from a foreign language, so it is written in katakana.

Katakana is commonly used for:

• foreign loanwords
• foreign names
• sound effects
• emphasis in some cases

So デュエット is the Japanese pronunciation of duet.

A native English speaker may also notice that Japanese pronunciation adds vowels and adjusts sounds to fit Japanese phonetics, which is why duet becomes デュエット.

It is pronounced roughly like dyu-etto.

Breaking it down:

• デュ = dyu
• エ = e
• ット = tto

A couple of useful points:

• ュ is a small kana, so デュ is one combined sound, not de-yu
• ッ is the small tsu, which marks a doubled consonant, so the t in ット is held slightly

So it is not pronounced exactly like English duet. It is adapted to Japanese sound patterns.

Japanese normally does not use spaces between words in ordinary writing.

So this would usually be written as:

デュエットを歌おう。

If you see spaces, they are often there for learners to make the sentence easier to read. They are not wrong in teaching materials, but they are not standard in normal Japanese text.

Not naturally in this sentence.

• を marks what is being sung
• で usually marks means, location, or the setting/manner of an action

So デュエットを歌おう means let’s sing a duet, where duet is the thing performed.

If you used デュエットで, it would suggest something more like as a duet or in a duet style, but that is not the normal way to say this basic idea.

For this sentence, を is the natural choice.

It can be used with both songs and singing performances.

Common examples:

• 歌を歌う = sing a song
• 演歌を歌う = sing enka
• アニメソングを歌う = sing an anime song
• デュエットを歌う = sing a duet

So Japanese allows 歌う with not only a specific song title but also a type or style of singing performance.

In very casual speech, particles are sometimes dropped, so you might hear:

デュエット歌おう。

But the full standard form is:

デュエットを歌おう。

For learners, it is best to use the particle until you get comfortable with when omission sounds natural. In writing and careful speech, keeping を is the safest choice.