Han spiller videre for ikke å bli stille under sceneskiftet.

Spiller videre means keeps playing, continues playing, or plays on.

• spiller = plays / is playing
• videre = further, on, onward

When videre is used with a verb like this, it often gives the idea that the action does not stop. So han spiller videre is not just he plays; it is he keeps playing.

Yes. Han fortsetter å spille is a very natural alternative and means almost the same thing: he continues to play.

There is a small nuance:

• spiller videre sounds a bit more like plays on / keeps going
• fortsetter å spille is the more direct continues to play

In many contexts, either would work.

For ikke å introduces a purpose: in order not to or so as not to.

So:

• for å ... = in order to ...
• for ikke å ... = in order not to ...

In this sentence, for ikke å bli stille means in order not to become quiet/silent.

It tells you why he keeps playing.

With for + infinitive to express purpose, for ikke å + infinitive is the standard and very common pattern.

So:

• for ikke å bli
• for ikke å glemme
• for ikke å stoppe

In other kinds of infinitive phrases, you will often see å ikke + verb instead, for example:

• Det er viktig å ikke glemme.

So this word order is something worth learning as a set pattern: for ikke å ...

Because bli means become, while være means be.

• bli stille = become quiet / go silent
• være stille = be quiet / be silent

Here the idea is that he keeps playing so that things do not go quiet during the scene change. That change into silence is why bli fits better than være.

Here stille means quiet or silent.

Norwegian stille can have several related meanings depending on context, such as:

• quiet
• silent
• calm
• sometimes still

In this sentence, because it is about playing during a scene change, the natural meaning is silent/quiet in an audio sense.

Because Norwegian usually marks definiteness by adding it to the end of the noun.

• et sceneskifte = a scene change
• sceneskiftet = the scene change

The ending -et is the definite ending for this neuter noun.

So under sceneskiftet literally works as during the scene change.

Here under means during, not underneath.

So:

• under sceneskiftet = during the scene change

Norwegian under can mean both under/below and during, and context tells you which meaning is intended. In this sentence, time is meant, not physical position.

Most likely, yes. Because it says sceneskiftet with the definite form, it usually points to the scene change in a specific situation.

If it were more general or indefinite, you might instead see:

• under et sceneskifte = during a scene change

So the definite form suggests a particular scene change that the speaker and listener can identify from context.

Yes. In this kind of sentence, han is understood as the subject of the whole idea.

So grammatically, it is he who:

• spiller videre
• does so for ikke å bli stille

That is very normal in Norwegian infinitive purpose phrases. The subject of the main clause is usually understood as the subject of the infinitive phrase unless context clearly suggests something else.