wǒ hé péngyou zhèngzài héchàng.

In Chinese, 我和朋友 can naturally mean my friend and I even without saying 我的朋友.

That is because in many contexts, the relationship is understood from the sentence. If you say:

• 我和朋友...

listeners will usually understand it as I and my friend / my friends...

If you want to be more explicit, you can say:

• 我和我的朋友正在合唱。

That is also correct, but it is a little more specific and slightly less economical.

Here, 和 means and.

So:

• 我和朋友 = I and my friend / my friends

In other sentences, 和 can also behave a bit like with, depending on the structure, but in this sentence it is clearly joining two nouns, so and is the best way to understand it.

Common alternatives include:

• 我跟朋友正在合唱。
• 我和朋友正在合唱。

Both are natural.

正在 shows that an action is in progress right now.

So:

• 合唱 = to sing together / perform choral singing
• 正在合唱 = are in the middle of singing together

This is similar to the English idea of am/is/are ...-ing.

Structure:

• subject + 正在 + verb

Examples:

• 我正在吃饭。 = I am eating.
• 他们正在聊天。 = They are chatting.
• 我和朋友正在合唱。 = My friend and I are singing together right now.

All three can mark an ongoing action, but 正在 is the clearest and most explicit.

• 在
  • verb
• 正
  • verb
• 正在
  • verb

Examples:

• 我在看书。
• 我正看书。
• 我正在看书。

All can mean I am reading.

For learners, 正在 is often easiest to understand because it strongly emphasizes right now / in progress.

In your sentence:

• 我和朋友在合唱。 — possible
• 我和朋友正合唱。 — possible, but less common in beginner-style speech
• 我和朋友正在合唱。 — very clear and natural

合唱 usually refers to singing together in a coordinated way, especially choral singing or a group vocal performance.

It is not just any kind of singing. It suggests that multiple people are singing the same piece together.

Depending on context, it can mean:

• to sing in chorus
• to sing together
• choral singing

A learner should know that 合唱 is more specific than 唱歌.

Compare:

• 我和朋友正在唱歌。 = My friend and I are singing.
• 我和朋友正在合唱。 = My friend and I are singing together as a coordinated vocal performance.

So if you just mean we are singing songs together casually, 唱歌 may sound more natural.

Yes.

As a verb, it means to sing together / perform choral singing:

• 我们正在合唱。

As a noun, it can mean chorus / choral singing:

• 我喜欢合唱。 = I like choral singing.

Chinese often allows the same word to function in more than one way depending on context.

Yes, that is also correct.

Compare:

• 我和朋友正在合唱。
• 我正在和朋友合唱。

Both are natural.

The difference is mainly one of focus:

• 我和朋友正在合唱。
  Focuses first on who is involved: my friend and I
• 我正在和朋友合唱。
  Focuses first on what I am doing: I am currently singing with a friend

Both are grammatically fine.

No, you do not need 一起 here.

Because 合唱 already contains the idea of doing it together, adding 一起 is often unnecessary.

• 我和朋友正在合唱。 — already complete and natural

You could say:

• 我和朋友正在一起唱歌。

But with 合唱, 一起 can sound a bit redundant unless you want extra emphasis on togetherness.

The sentence is grammatical and understandable, but whether it sounds fully natural depends on what you mean.

If you mean a formal or organized musical activity, 合唱 works well:

• 我和朋友正在合唱。

If you just mean my friend and I are singing together, many native speakers might more naturally say:

• 我和朋友正在唱歌。
• 我正在和朋友一起唱歌。

If you mean a chorus performance, you might also hear something more specific like:

• 我和朋友正在合唱一首歌。
• 我们正在参加合唱。

So the sentence is fine, but 合唱 is a bit more specialized than simple singing.

Chinese nouns usually do not change form for singular vs. plural the way English nouns do.

So 朋友 can mean:

• friend
• friends

The exact meaning depends on context.

So:

• 我和朋友正在合唱。

could mean:

• My friend and I are singing together
• My friends and I are singing together

If you want to make plurality clearer, you can say:

• 我和一个朋友正在合唱。 = I am singing together with one friend.
• 我和几个朋友正在合唱。 = I am singing together with several friends.

A few pronunciation points are useful here:

• 我 = wǒ (3rd tone)
• 和 = hé (2nd tone, in this sentence)
• 朋友 = péngyou
  
  • péng is 2nd tone
  • you is often neutral in normal speech
• 正在 = zhèngzài (4th tone + 4th tone)
• 合唱 = héchàng (2nd tone + 4th tone)

Two especially useful notes:

1. 朋友 is commonly pronounced péngyou, with the second syllable light.
2. 和 has multiple pronunciations in Chinese, but here it is pronounced hé.

No. Standard written Chinese normally does not put spaces between words.

So the normal sentence is:

• 我和朋友正在合唱。

The spaces in learning materials are only there to help beginners see the word boundaries:

• 我 / 和 / 朋友 / 正在 / 合唱

That is a teaching tool, not standard Chinese punctuation or spacing.

Yes. 跟 is a very common spoken alternative.

For example:

• 我跟朋友正在合唱。

This is very natural in everyday speech.

In many situations:

• 和 sounds slightly more neutral or written
• 跟 sounds a bit more conversational

Both are very common and correct.