Quando eu escuto música, tenho vontade de cantar.

Quando means when. It introduces a time clause:

• Quando eu escuto música = When I listen to music

In Portuguese, just like in English, a sentence can begin with this kind of time expression.

Yes, eu can be omitted here.

Portuguese often leaves out subject pronouns when the verb ending already makes the subject clear:

• Quando eu escuto música, tenho vontade de cantar.
• Quando escuto música, tenho vontade de cantar.

Both are natural.
Including eu can add a little emphasis or clarity, but it is not necessary.

Escuto is the 1st person singular present tense of escutar:

• eu escuto = I listen / I hear

In this sentence, it means I listen to.

So:

• Quando eu escuto música = When I listen to music

Yes. That is very common.

Portuguese has both:

• escutar
• ouvir

So you can say:

• Quando eu escuto música...
• Quando eu ouço música...

Both are natural in Brazilian Portuguese.
Ouvir is often a little more common in everyday speech, but escutar is also widely used.

Note that ouvir is irregular:

• eu ouço = I hear / I listen

not eu ovo or anything like that.

Because Portuguese does not use the same structure as English here.

In English, we say:

• listen to music

But in Portuguese, the verb can take the object directly:

• escutar música
• ouvir música

So you do not need a separate word matching English to.

Portuguese often uses nouns without an article when speaking in a general sense.

So:

• escuto música = I listen to music in general

You could say escuto a música in some specific contexts, but that usually means the music or a particular piece/song.

Here, música is general, so no article is the most natural choice.

Ter vontade de is a very common expression meaning:

• to feel like
• to want to
• to have the urge/desire to

So:

• tenho vontade de cantar = I feel like singing / I want to sing

Literally, it is something like:

• I have desire to sing

But in natural English, I feel like singing is often the best translation.

Because the expression is:

• ter vontade de + infinitive

So the pattern is:

• tenho vontade de comer
• tenho vontade de dormir
• tenho vontade de viajar
• tenho vontade de cantar

The de belongs to the expression. After vontade, if you follow it with a verb, that verb normally comes in the infinitive.

Because after tenho vontade de, Portuguese uses the infinitive to express the action someone feels like doing.

• cantar = to sing

So:

• tenho vontade de cantar = I feel like singing

This is very similar to English structures like:

• want to sing
• feel like singing

Portuguese uses de + infinitive here.

Because the sentence describes a general, repeated situation:

• When I listen to music, I feel like singing.

This is not about one specific moment only. It expresses something that usually happens, so the present tense is natural in Portuguese.

• escuto = I listen
• tenho = I have / I feel

The comma separates the time clause from the main clause:

• Quando eu escuto música, = time/background
• tenho vontade de cantar. = main idea

This is also common in English:

• When I listen to music, I feel like singing.

So the comma helps mark the pause between the two parts.

It is neutral and natural. You can use it in normal conversation and in writing.

Nothing in the sentence is especially formal or slangy. It is a standard, everyday way to express the idea.

Yes, and that sounds very natural too.

• Quando ouço música, dá vontade de cantar.

This literally works more like:

• When I listen to music, it gives the urge to sing
• more naturally: When I listen to music, I feel like singing

This version is a bit more impersonal, while tenho vontade de cantar is more directly I feel like singing.

Both are common in Brazilian Portuguese.

Vontade is very useful. Some common expressions are:

• Tenho vontade de viajar. = I feel like traveling.
• Estou com vontade de comer pizza. = I feel like eating pizza.
• Que vontade de dormir! = I really feel like sleeping!
• Fique à vontade. = Make yourself comfortable / Feel free.

So vontade often relates to desire, willingness, or feeling like doing something.