A afinação muda com o ritmo.

In Portuguese, it is very common to use a definite article before a noun, even when English would often leave it out.

So a afinação literally means the tuning / the intonation / the pitch, but in many contexts Portuguese uses the article more naturally than English does.

Also, afinação is a feminine noun, so it takes a, not o.

• a afinação
• a música
• a melodia

This is one of those places where Portuguese simply sounds more natural with the article.

Afinação usually refers to tuning, intonation, or pitch accuracy, depending on context.

Possible uses:

• in music, the tuning of an instrument
• in singing, whether someone is singing in tune
• more generally, pitch/intonation quality

So in this sentence, the exact best translation depends on context:

• The tuning changes with the rhythm
• The pitch changes with the rhythm
• The intonation changes with the rhythm

If the sentence is about a singer or melody, intonation or pitch may fit better. If it is about an instrument, tuning may fit better.

Here, muda is a verb: the third-person singular form of mudar (to change).

So:

• A afinação muda = The tuning/intonation changes

This is different from the adjective/noun mudo / muda, which can mean mute or silent depending on context.

In this sentence, you can tell it is a verb because it follows the subject:

• A afinação = subject
• muda = verb

It is in the present indicative.

From the verb mudar:

• eu mudo
• você/ele/ela muda
• a afinação muda

This present tense can express:

• a general fact
• a habitual action
• something happening now, depending on context

Here it sounds like a general statement:

• The tuning changes with the rhythm

Com means with.

So:

• com o ritmo = with the rhythm

This phrase shows what the change happens along with, or what it varies together with.

It suggests something like:

• as the rhythm changes, the tuning changes too
• the tuning varies according to the rhythm

Portuguese often uses com in this kind of sentence where English might also say:

• with
• according to
• along with

Again, Portuguese often uses the definite article where English might not.

So o ritmo is very natural here.

Even when speaking generally, Portuguese commonly says:

• o ritmo
• a música
• a temperatura
• o tempo

English sometimes drops the article in broader statements, but Portuguese usually keeps it.

No. Com o stays com o.

Unlike:

• de + o = do
• em + o = no
• a + o = ao

the preposition com normally does not contract in standard modern Portuguese writing.

So the correct standard form is:

• com o ritmo

You may hear very reduced pronunciation in fast speech, but in writing it remains com o.

A helpful approximate pronunciation in Brazilian Portuguese is:

ah-fee-nah-SOWN

A few details:

• afi- sounds like ah-fee
• na is unstressed and light
• ção is a very common ending, pronounced roughly like sown with a nasal sound

The stress is on the last syllable:

• a-fi-na-ÇÃO

That final ão is nasal, which is important in Brazilian Portuguese.

In Brazilian Portuguese, ritmo is roughly:

HEET-mo or HIT-mo, depending on accent and speed

A few notes:

• the r at the start of a word is usually a strong Brazilian r, often somewhat like an English h sound
• the i is like ee
• the tmo cluster can feel a little tight for English speakers, but Brazilians say it smoothly

So it does not sound exactly like English rhythm.

Yes. Portuguese allows some flexibility.

The original order:

• A afinação muda com o ritmo.

You could also say:

• Com o ritmo, a afinação muda.

That version gives a little more emphasis to com o ritmo.

The original sentence is the most neutral and straightforward.

Yes, and it changes the feel slightly.

• A afinação muda com o ritmo = a general fact or regular pattern
• A afinação está mudando com o ritmo = it is changing right now

So if you are describing something in progress, está mudando is very natural. If you are stating a general principle, muda is usually better.

Yes.

• afinar = to tune, to bring into tune
• afinação = tuning, intonation, pitch accuracy

This is a very common pattern in Portuguese:

• verb + noun form

For example:

• organizar → organização
• combinar → combinação
• afinar → afinação

So if you know afinar, it is easier to remember afinação.

Yes, it is grammatical and natural.

It sounds like something you might say in a musical, technical, or descriptive context. The only thing that depends on context is the exact meaning of afinação:

• tuning
• pitch
• intonation

So the sentence itself is fine; you just choose the best English interpretation based on what is being discussed.