La salida de escena permite el cambio de escena.

Because salida is a noun, while salir is a verb.

• salir de escena = to leave the stage / to exit the scene
• la salida de escena = the exit from the stage / the act of leaving the scene

In this sentence, Spanish needs a noun phrase as the subject of permite, so la salida de escena works naturally.

Salida usually means exit, way out, or departure. In this context, it refers to the act of going offstage or the exit from the scene.

So here it is not just a physical door or exit sign. It means something more like:

• the exit
• the actor’s departure
• going offstage

The exact nuance depends on the theatrical context.

Here, de links the noun salida to what the exit is from.

So:

• salida de escena = exit from the scene/stage
• literally, exit of/from scene

This is very common in Spanish. Compare:

• cambio de ropa = change of clothes
• fin de semana = weekend
• puerta de casa = the door of the house / house door

In this sentence, de escena tells us what kind of exit it is.

Because the subject is singular: la salida.

Even though the phrase is longer, the core subject is still just one thing:

• La salida de escena = singular

So the verb must also be singular:

• La salida de escena permite...

If the subject were plural, then you would use permiten:

• Las salidas de escena permiten...

All three are possible depending on the translation style.

Permitir often means:

• to allow
• to permit
• to make possible

In this sentence, allows or makes possible sounds especially natural in English:

• The exit from the stage allows the scene change
• The exit from the stage makes the scene change possible

Because Spanish often uses noun phrases where English might also use a noun phrase.

• el cambio de escena = the scene change
• cambiar de escena = to change scene / to change to another scene

After permite, both a noun phrase and an infinitive can be possible in Spanish, but they mean slightly different things.

Here, permite el cambio de escena focuses on the event or process of the scene change itself.

It can suggest either one depending on context, especially in theatre language.

Most directly, escena means scene. But in expressions like salir de escena, it often means to leave the stage or go offstage.

So:

• salida de escena can mean exit from the scene or going offstage
• cambio de escena usually means scene change

The first escena may feel closer to stage performance space, while the second clearly points to scene in the theatrical sense.

Because Spanish generally uses articles more often than English.

Here, both noun phrases refer to specific ideas:

• la salida de escena = the exit from the stage/scene
• el cambio de escena = the scene change

Even when English might sometimes omit an article in a more general style, Spanish often keeps it.

Yes, it is normal. Spanish often repeats a phrase if it helps keep the meaning clear.

Here the two parts refer to two related but different things:

• salida de escena = going offstage
• cambio de escena = scene change

So the repetition is not necessarily bad style. It may even be useful because it keeps the theatrical context explicit.

That said, in a different context, a writer might rephrase it to avoid repetition if style matters more.

Yes, that is possible, and it changes the nuance a little.

• escenario = stage as the physical stage
• escena = scene, and sometimes stage presence in theatrical language

So:

• salida de escena sounds more theatrical/idiomatic
• salida del escenario sounds more concrete and physical: exit from the stage

Both can work, but salida de escena is a very natural expression in performance-related Spanish.

In standard Peninsular Spanish, a rough pronunciation would be:

la sa-LI-da de es-CE-na per-MI-te el CAM-byo de es-CE-na

A few notes for Spain:

• c before e in escena is pronounced like the th in thin in most of Spain.
• cambio has a clear k sound at the start: KAM-byo
• ll is usually pronounced like a y sound in modern Spanish, though that does not appear in this sentence.

So escena in Spain sounds roughly like es-THE-na.