A todo esto, preparaban la pista de baile.

It is a fixed expression used to give background or add something happening at the same time as other events. In this kind of sentence, it often means something like meanwhile, all this time, or by the way, in the middle of all that.

It does not usually mean the literal sum of a + todo + esto word by word. As a chunk, it works like a discourse marker.

For example, it can introduce information such as:

• while all that was going on...
• in the meantime...
• during all this...

So here it helps place preparaban la pista de baile in the wider scene.

Because the imperfect (preparaban) is often used for:

• background actions
• ongoing actions in the past
• descriptions of what was happening
• actions without a clear beginning or end in focus

So preparaban presents the action as in progress or as part of the background scene.

By contrast, prepararon (preterite) would present it more as a completed event: they prepared it, and that action is viewed as finished.

A learner-friendly contrast is:

• A todo esto, preparaban la pista de baile.
  = this was going on in the background / they were in the process of preparing it

• A todo esto, prepararon la pista de baile.
  = they prepared it (as a completed action)

Yes. Estaban preparando la pista de baile is also possible.

The difference is subtle:

• preparaban = simple imperfect; often sounds more narrative and compact
• estaban preparando = imperfect of estar
  • gerund; it emphasizes more clearly that the action was actively in progress at that moment

In many contexts, both are natural. Spanish often prefers the simple imperfect where English might strongly prefer were preparing.

Spanish often leaves out subject pronouns when the verb ending already makes the subject clear.

Preparaban tells you the subject is:

• they
• or you (plural) in some varieties

In standard Peninsular Spanish, in a normal narrative sentence like this, the most natural reading is they were preparing.

Spanish does this all the time:

• Llegaron tarde. = They arrived late.
• No sabían qué hacer. = They didn’t know what to do.

You only add ellos/ellas if you want emphasis, contrast, or clarity.

Because the verb agrees with an implied plural subject.

The ending -aban in preparaban shows:

• imperfect tense
• third person plural

So the sentence implies they were preparing the dance floor.

If it were singular, you would get:

• preparaba = he/she/it was preparing

Pista de baile means dance floor.

Literally:

• pista = floor/track/area/platform, depending on context
• de baile = for dancing / of dancing

As a whole, pista de baile is the normal expression for a dance floor.

Examples:

• La pista de baile estaba llena. = The dance floor was full.
• Abrieron la pista de baile a medianoche. = They opened the dance floor at midnight.

Spanish uses articles more often than English.

Here, la pista de baile sounds natural because it refers to a specific dance floor in the situation being described — the one at the party, venue, event, etc.

English often drops the article in places where Spanish keeps it:

• Voy al hospital / I’m going to hospital or to the hospital
• Preparaban la pista de baile / They were preparing the dance floor

Without the article, preparaban pista de baile would sound wrong in standard Spanish.

You should learn it mainly as one chunk.

Even though the words individually are simple, the meaning of the full expression is idiomatic. Native speakers do not usually process it literally as to all this.

That is very common in Spanish:

• sin embargo
• de repente
• por cierto
• a todo esto

So it is best to store A todo esto as a fixed expression used to move the narrative along.

Because A todo esto works like a sentence adverbial or discourse marker. It sets the scene for the rest of the sentence rather than being part of the core verb phrase.

The comma helps show that structure:

• A todo esto, preparaban la pista de baile.

It is similar to commas after expressions like:

• Mientras tanto, ...
• Por cierto, ...
• Sin embargo, ...

In short, the comma marks a pause and shows that A todo esto introduces the context.

Yes, Spanish word order is flexible, though some versions sound more natural than others.

The original is very natural:

• A todo esto, preparaban la pista de baile.

You could also find:

• Preparaban la pista de baile, a todo esto.

But that version is less neutral and depends more on style or emphasis.

In ordinary narration, putting A todo esto at the beginning is the most natural choice.

It is understood across the Spanish-speaking world, but it is often felt as quite natural in Peninsular Spanish narrative style.

Depending on the country or context, speakers might also use other expressions with a similar job, such as:

• mientras tanto
• por cierto
• entre tanto
• en todo esto

The exact nuance changes, but A todo esto is definitely a useful expression to recognize, especially in Spanish from Spain.

It still basically means to prepare, but the exact real-world action depends on context.

With la pista de baile, it could mean things like:

• arranging the area
• clearing space
• setting up lights or music
• getting the dance floor ready for use

So the verb is general, and the noun phrase tells you what was being made ready.

Most likely background information.

Two clues point to that:

• A todo esto frames the sentence as part of the surrounding situation
• preparaban is in the imperfect, which often gives background in storytelling

So this sentence sounds like the narrator is saying what was happening in the meantime, while other events were unfolding.