A plateia segue a batida, só que a acústica tem eco.

Because segue is the conjugated form of the verb seguir in the present tense.

• seguir = infinitive, to follow
• a plateia = the subject
• a plateia segue = the audience follows

Since plateia is singular, the verb is singular too.

Plateia is a collective noun. It refers to a group of people as one unit, much like audience in English.

So in Portuguese, it normally takes a singular verb:

• A plateia segue...
• not A plateia seguem...

They are similar, but not always identical.

• plateia usually means the audience, especially at a show, theater, concert, or event
• público can also mean audience, but it is broader and can mean the public in general

In this sentence, plateia fits well because it suggests people listening together in a performance setting.

That a is the feminine singular definite article, meaning the.

• a plateia = the audience
• a batida = the beat
• a acústica = the acoustics

All three nouns are feminine singular, so they use a.

Because seguir is usually a direct transitive verb in this meaning. It takes a direct object without a preposition.

So:

• seguir a batida = to follow the beat
• seguir o ritmo = to follow the rhythm

This is normal Portuguese usage.

Here, batida means the beat or rhythmic pulse of the music.

This word can have other meanings in other contexts, such as:

• a collision/crash
• a blended drink
• a knocking or hitting sound

But in a musical sentence like this one, batida is naturally understood as beat.

Só que is a very common Brazilian Portuguese connector meaning something like:

• but
• except that
• the thing is

It is a bit more conversational than mas.

So:

• ..., só que ... sounds natural and spoken
• ..., mas ... would also be correct, but slightly more neutral or straightforward

Because só que introduces a contrasting idea.

The sentence has two parts:

• A plateia segue a batida
• só que a acústica tem eco

The comma helps separate those two clauses, just as you would often do before but in English.

Here, acústica means the acoustics of the place, meaning the way sound behaves in the room or venue.

So a acústica is not talking about an acoustic guitar here. Context makes it clear that it means the sound quality or sound properties of the space.

Portuguese often expresses this kind of idea differently from English.

A acústica tem eco literally looks like the acoustics have echo, but it sounds natural in Portuguese. It means that the room’s acoustics produce or contain echo.

You could also hear other expressions in Portuguese, depending on context, but tem eco is very natural in everyday Brazilian Portuguese.

Because eco is being used in a general, non-specific way.

• tem eco = has echo / there is echo
• tem um eco estranho = there is a strange echo
• tem o eco da sala = it has the echo of the room

Without an article, it sounds more general and natural here.

In standard Brazilian pronunciation, segue sounds roughly like SEH-ghee.

A few quick guides:

• plateia ≈ pla-TEI-a
• segue ≈ SEH-ghee
• batida ≈ ba-CHEE-da or ba-TEE-da, depending on accent
• acústica ≈ a-KOOS-chi-ka
• eco ≈ EH-ko

The exact pronunciation can vary by region, but those approximations are useful for a learner.