Au vide-grenier, le brocanteur vend un vinyle avec une rayure.

Because au is the required contraction of à + le in French.

• à + le = au
• à + les = aux

So au vide-grenier means at the flea market / at the garage-sale event.

This is the same pattern as:

• au marché
• au restaurant
• au cinéma

A vide-grenier is a kind of second-hand sale where people sell old things they no longer want. Literally, it means empty-attic.

For an English speaker, it is often closest to:

• a garage sale
• a yard sale
• sometimes a flea market

But the exact feel is slightly different depending on the country and context. In France, a vide-grenier is often a local community event where ordinary people sell used belongings.

It is a masculine noun: le vide-grenier.
Plural: les vide-greniers.

A brocanteur is a person who buys and sells second-hand objects, old furniture, collectibles, or antiques.

It is more specific than just seller. A brocanteur is usually someone connected with the second-hand or antique trade.

So:

• vendeur = seller, salesperson
• brocanteur = second-hand dealer / antique dealer / junk dealer, depending on context

French often uses the definite article when the person is seen as identifiable in the situation.

So le brocanteur can mean something like:

• the dealer
• the second-hand seller there

Even if English might naturally say a dealer, French can use le when the role is clear from the context.

If you said un brocanteur, it would sound more like you are introducing one dealer among others for the first time. Both are possible, but they are not exactly the same in tone.

Yes. In everyday French, un vinyle commonly means a vinyl record.

You can also say:

• un disque vinyle

That is a little more explicit, but un vinyle is very common.

Context matters, because vinyle can also refer to the material vinyl. But in this sentence, it clearly means the record.

Because here vinyle means one vinyl record, which is a countable object.

• un vinyle = a vinyl record
• du vinyle = some vinyl, the material

So the sentence is talking about one item being sold, not the substance it is made of.

Here une rayure means a scratch on the record.

That is important because rayure can also mean stripe in other contexts. For example, on clothing, des rayures are stripes. But with a record, une rayure is understood as a scratch or surface mark.

So in this sentence, avec une rayure means the record has a scratch.

Yes, absolutely.

• un vinyle avec une rayure = a vinyl record with a scratch
• un vinyle rayé = a scratched vinyl record

Both are correct.
avec une rayure emphasizes the scratch as a separate detail.
rayé is a more compact adjective-based way to say it.

In many situations, un vinyle rayé may sound a little more natural.

It sets the scene first, like saying:

• At the flea market, ...

French often puts a time or place phrase at the beginning when it gives the background for the rest of the sentence.

So:

• Au vide-grenier, le brocanteur vend un vinyle avec une rayure.

means the speaker first tells you where the action is happening, then tells you who is doing what.

The comma helps separate that introductory setting from the main clause.

It is grammatically correct and understandable, but there is a small nuance.

A vide-grenier is often associated with ordinary people selling their own used belongings, while a brocanteur sounds more like a professional second-hand dealer.

So the combination is possible, but it may feel slightly marked depending on the context.

If you wanted something that sounds a bit more typical, you might hear:

• Au vide-grenier, un vendeur vend un vinyle rayé.
• À la brocante, le brocanteur vend un vinyle rayé.

But the original sentence is still perfectly workable French.

Roughly, it sounds like:

• veed gruh-nyay

A few helpful points:

• vide sounds like veed
• grenier ends with a sound like nyay
• the r is the French r, produced farther back in the throat than in English

Also, the final r of vide is not there, because the word is vide, not vider. So keep it short and clean: veed-gruh-nyay.