Сначала нужно распеться.

Here сначала means first, to begin with, or before anything else.

So the sentence has the sense of:

First, it’s necessary to warm up the voice.

A useful nuance:

• сначала = first / at first / to begin with
• In this sentence, it clearly means the first thing to do is...

Russian often uses impersonal constructions where English would normally supply a subject.

In Сначала нужно распеться, the word нужно means it is necessary / one needs to. Because of that, Russian does not have to say exactly who needs to do it.

Depending on context, it could mean:

• I need to warm up first
• We need to warm up first
• You need to warm up first
• First, it’s necessary to warm up

Russian leaves the subject unstated when it is obvious from the situation or when the statement is meant generally.

Нужно means necessary, needed, or one needs to.

In sentences like this, it works as part of a very common pattern:

нужно + infinitive

So:

• нужно распеться = it’s necessary to warm up one’s voice

Similar examples:

• Нужно идти. = We need to go.
• Нужно подождать. = It’s necessary to wait.

It is a very common neutral way to express necessity.

Because after нужно, Russian usually uses an infinitive.

Structure:

• нужно
  • verb in infinitive

So:

• нужно распеться not
• нужно распелся not
• нужно распоётся

The infinitive is the dictionary form of the verb, similar to English to sing, to wait, to go.

Петь simply means to sing.

Распеться means something more specific: to sing until the voice opens up / to warm up vocally / to get into singing form.

So the idea is not just to sing, but:

• to loosen the voice,
• to get comfortable,
• to reach better vocal condition.

This is why распеться is often used for singers before a performance or rehearsal.

The -ся ending marks a reflexive verb.

In many Russian verbs, -ся does not always mean a direct English-style reflexive like wash oneself. Sometimes it changes the meaning in a more idiomatic way.

Here:

• распеть is not what is meant
• распеться is the established verb meaning to warm up one’s voice by singing

So in this case, -ся is just part of the normal dictionary form of the verb you need to learn.

This is about aspect.

• распеться = perfective
• распеваться = imperfective

In this sentence, распеться is used because the idea is to achieve the result of being vocally warmed up.

So:

• Сначала нужно распеться. = First, you need to get your voice warmed up.

If you used распеваться, it would focus more on the process:

• Нужно распеваться перед концертом. = You need to do vocal warm-ups before a concert.

So распеться here emphasizes the completed preparation.

Yes, it is very natural.

It sounds like something someone might say:

• before singing,
• before rehearsal,
• before recording,
• before going on stage.

It is concise and idiomatic. Russian often prefers short impersonal sentences like this.

Yes, Russian word order is flexible.

For example:

• Сначала нужно распеться.
• Нужно сначала распеться.

Both are natural.

The difference is mostly one of emphasis:

• Сначала нужно распеться. emphasizes first
• Нужно сначала распеться. emphasizes the necessity a little more, while still keeping first in the sentence

In neutral speech, both are fine.

Technically, сначала can sometimes be translated as at first, but in this sentence first / first of all is the better interpretation.

Compare:

• Сначала было трудно. = At first, it was difficult.
• Сначала нужно распеться. = First, you need to warm up your voice.

So the exact English translation depends on context, but here it clearly introduces the first step.

The stress is:

• снача́ла
• ну́жно
• распе́ться

That last one is important: распе́ться, not ра́спеться.

Yes. Надо is very close in meaning.

So:

• Сначала нужно распеться.
• Сначала надо распеться.

Both are natural and both mean roughly the same thing.

A rough guide:

• нужно can sound a little more neutral or formal
• надо can sound a little more conversational

But in everyday use, they overlap a lot.

Yes. A very literal breakdown would be:

• Сначала = first
• нужно = it is necessary
• распеться = to warm up one’s voice by singing

So literally:

First, it is necessary to warm up one’s voice.

That kind of literal breakdown helps explain the grammar, even if the natural English translation might be something like:

First, you need to warm up your voice.