Kiedy ona słucha muzyki w salonie, ja czytam książkę w sypialni.

That’s true: Polish usually does not need subject pronouns because the verb ending already shows who is doing the action.

• słucha = he/she/it listens
• czytam = I read

So the sentence could also be:

Kiedy słucha muzyki w salonie, czytam książkę w sypialni.

Adding ona and ja gives extra contrast or emphasis, something like:

• When she listens to music in the living room, I read a book in the bedroom.

So here the pronouns help highlight the difference between the two people.

Because the verb słuchać normally takes the genitive case, not the accusative.

So:

• muzyka = base form / nominative
• muzyki = genitive

That is why we say:

• słucha muzyki = listens to music

This is something you mainly need to memorize with the verb słuchać. Not every verb meaning “do something to an object” takes the accusative in Polish.

Because czytać usually takes the accusative case for its direct object.

So:

• książka = nominative
• książkę = accusative

Therefore:

• czytam książkę = I am reading / I read a book

This contrasts nicely with słuchać, which takes genitive:

• słucha muzyki
• czyta książkę

Because after w meaning in, when it shows location, Polish uses the locative case.

So:

• salon → w salonie
• sypialnia → w sypialni

These mean:

• in the living room
• in the bedroom

If there were movement into a room, Polish would often use a different case:

• idę do salonu = I’m going to the living room

But here there is no movement, only location, so we use w + locative.

Here kiedy can be understood as when or while, depending on how natural the English translation is.

In this sentence, it introduces a time clause:

• Kiedy ona słucha muzyki w salonie, ja czytam książkę w sypialni.

This can mean:

• When she listens to music in the living room, I read a book in the bedroom.
• While she is listening to music in the living room, I am reading a book in the bedroom.

So kiedy is a general time word. Context tells you whether it sounds more like when, whenever, or while.

Because Kiedy ona słucha muzyki w salonie is a subordinate clause, and in Polish subordinate clauses are normally separated by a comma.

Structure:

• Kiedy ona słucha muzyki w salonie, = subordinate time clause
• ja czytam książkę w sypialni. = main clause

Polish punctuation is stricter than English here. Even if English sometimes feels more flexible, Polish definitely requires the comma.

Yes. Polish word order is much more flexible than English word order because cases and verb endings show the grammatical relationships.

The original sentence is natural:

• Kiedy ona słucha muzyki w salonie, ja czytam książkę w sypialni.

But you could also hear versions like:

• Ja czytam książkę w sypialni, kiedy ona słucha muzyki w salonie.
• W sypialni czytam książkę, kiedy ona słucha muzyki w salonie.

The meaning stays similar, but the focus changes. The original version is a neutral, clear way to say it.

They are both in the present tense.

• słucha = she listens / she is listening
• czytam = I read / I am reading

Polish present tense can cover both:

• a habitual meaning: she listens, I read
• an ongoing meaning: she is listening, I am reading

Context decides which is more natural in English.

Yes. Polish present tense often works for both habitual actions and actions happening now.

So the sentence could mean either:

• Whenever she listens to music in the living room, I read a book in the bedroom. or
• While she is listening to music in the living room, I am reading a book in the bedroom.

Without extra context, both are possible.

Because Polish does not have articles like English a/an/the.

So:

• muzyki could mean music
• książkę could mean a book or the book, depending on context
• w salonie = in the living room / in a living room
• w sypialni = in the bedroom / in a bedroom

Context tells you whether something is definite or indefinite.

In the Polish present tense, the 3rd person singular usually has one form for all three:

• on słucha = he listens
• ona słucha = she listens
• ono słucha = it listens

So the verb form itself does not show gender here. The pronoun does:

• on = he
• ona = she
• ono = it

That’s one reason pronouns can sometimes be useful for clarity, even though they are often omitted.

Yes, very often you can.

A very natural shorter version is:

• Kiedy słucha muzyki w salonie, czytam książkę w sypialni.

This is grammatically fine because:

• słucha already implies she/he/it
• czytam already implies I

However, without ona, the first verb could theoretically mean he/she/it listens, so the pronoun may be kept if the speaker wants to be explicit. Keeping both ona and ja also makes the contrast clearer.

Yes. In everyday Polish, salon commonly means living room.

So:

• w salonie = in the living room

And:

• sypialnia = bedroom
• w sypialni = in the bedroom

So the room vocabulary in this sentence is completely natural.

Because Polish does not have a separate tense built like English be + -ing.

Instead, the ordinary present tense does the job:

• ona słucha = she listens / she is listening
• ja czytam = I read / I am reading

If you want to know whether the action is habitual or happening right now, you usually rely on context, not on a special continuous form.

Yes: they show two different patterns that are very useful for learners.

1. słuchać takes the genitive:

   • słucha muzyki

2. czytać takes the accusative:

   • czyta książkę

So this one sentence is a good reminder that in Polish, you cannot always assume every direct object will be in the same case. Different verbs may require different cases.