Quando eu escuto música, fico mais tranquilo.

Quando means when. In this sentence, it introduces a repeated or habitual situation:

• Quando eu escuto música, fico mais tranquilo.
• When I listen to music, I become / feel calmer.

It does not refer only to one specific moment. In Portuguese, quando is often used for general habits too, just like when in English.

Yes, eu can be left out:

• Quando eu escuto música, fico mais tranquilo.
• Quando escuto música, fico mais tranquilo.

Both are correct.

Portuguese often drops subject pronouns because the verb ending already shows who the subject is. Here, escuto clearly means I listen, and fico means I become / I feel.

Still, eu may be included for:

• emphasis
• clarity
• contrast

So using eu is natural, but not required.

In Portuguese, when speaking about something in a general sense, you often do not use the article.

So:

• escuto música = I listen to music in general

If you say:

• escuto a música

that usually sounds more specific, like:

• I listen to the song
• I listen to the music already mentioned or understood from context

So in this sentence, música is being used generally, which is why there is no article.

Yes. You could also say:

• Quando eu ouço música, fico mais tranquilo.

Both escutar and ouvir can mean to hear / to listen to in everyday Brazilian Portuguese.

Very roughly:

• ouvir is often the more common general verb
• escutar can sometimes feel a bit more like to listen, with attention

But in real usage, many speakers use them almost interchangeably in sentences like this. So escuto música and ouço música are both natural.

Here, ficar means something like:

• to become
• to get
• to end up feeling

So:

• fico mais tranquilo = I become calmer / I feel calmer

This is very common in Portuguese. Ficar is often used for a change of state:

• ficar feliz = to become happy
• ficar cansado = to get tired
• ficar nervoso = to get nervous

In this sentence, listening to music causes a change in mood, so ficar is the natural choice.

Because ser and ficar express different ideas.

• sou mais tranquilo = I am calmer / I’m a calmer person
  This sounds more like a general personality trait.

• fico mais tranquilo = I become calmer / I feel calmer
  This shows a change caused by listening to music.

So fico fits better because the sentence describes how music affects the speaker.

Mais tranquilo literally means more calm / calmer / more relaxed.

Depending on context, tranquilo can mean:

• calm
• relaxed
• at ease
• peaceful

So fico mais tranquilo could be understood as:

• I feel calmer
• I feel more relaxed
• I become more at ease

All of these are close in meaning.

Because the adjective must agree with the person being described.

If the speaker is male, they say:

• fico mais tranquilo

If the speaker is female, they say:

• fico mais tranquila

This is because tranquilo/tranquila changes for grammatical gender.

Because the sentence describes a general habit or repeated truth.

• escuto = I listen
• fico = I become / I feel

Portuguese often uses the simple present for things that happen regularly:

• Quando estudo, aprendo mais.
• When I study, I learn more.

So the present tense here means something like: Whenever I listen to music, I feel calmer.

The comma is standard and helpful here because the sentence begins with a subordinate clause:

• Quando eu escuto música, fico mais tranquilo.

The first part sets the condition/time frame, and the second part gives the result. In writing, the comma is normally used in this structure.

In speech, you may hear only a small pause or no strong pause at all, but in writing the comma is the normal choice.

Yes. You can also say:

• Fico mais tranquilo quando eu escuto música.

This means the same thing: I feel calmer when I listen to music.

The difference is mainly focus:

• Quando eu escuto música, ... starts with the situation
• Fico mais tranquilo ... starts with the result

Both are natural.

A simple approximate pronunciation is:

• escuto → eh-SKOO-too
• música → MOO-zee-kah or MYOO-zee-kah depending on accent
• tranquilo → trahn-KEE-loo

A few notes:

• The stress in música is on the first syllable: MÚ-si-ca
• The stress in tranquilo is on qui: tran-QUI-lo
• In Brazilian Portuguese, final -o often sounds close to oo in unstressed position

These are only approximations, but they can help at the beginning.

Yes, absolutely. It sounds natural and idiomatic.

A Brazilian might also say:

• Quando ouço música, fico mais tranquilo.
• Eu fico mais tranquilo quando escuto música.
• Quando escuto música, me sinto mais tranquilo.

All of these are normal. The original sentence is a very natural way to express the idea.