Стоит только добавить саундтрек, как короткометражка звучит иначе.

Here стоит is part of a fixed construction, not the literal idea of price.

Стоит только + infinitive, как + clause means something like:

• one only has to ... and ...
• as soon as ...
• it takes only ... for ... to happen

So:

Стоит только добавить саундтрек, как короткометражка звучит иначе.

means that just adding a soundtrack is enough for the short film to sound different.

In this pattern, стоит is impersonal. There is no real subject, and it does not mean costs in the usual sense.

Because after стоит только Russian normally uses an infinitive.

So the structure is:

• стоит только сделать что-то, как...

Here, добавить means to add.

The infinitive works well because the sentence is talking about an action in a general way, not about a specific person doing it. English often does the same with to add or with a generic you:

• You only have to add a soundtrack...
• One only has to add a soundtrack...

This is about aspect.

• добавить = perfective, a completed act of adding
• добавлять = imperfective, the process or repeated action of adding

In this sentence, the idea is that once the soundtrack has been added, the result appears immediately: the short film sounds different. That is why добавить is natural here.

With стоит только ... как ..., Russian very often uses the perfective infinitive when it means do it once, and this happens.

Только means only / just.

It emphasizes that the action is minimal or sufficient by itself:

• Стоит добавить саундтрек = it is enough to add a soundtrack
• Стоит только добавить саундтрек = you only have to add a soundtrack

So только adds the sense of that’s all it takes.

Yes, как often means how or like, but here it has a different function.

In the pattern стоит только ..., как ..., как introduces the consequence that follows immediately.

So here it is closer to:

• and then
• and immediately
• when / as soon as

This use is idiomatic. It is best to learn the whole pattern together:

• Стоит только X, как Y.

Russian often leaves the subject unstated when the meaning is general.

Here the sentence does not focus on who adds the soundtrack. It means something like:

• if you add a soundtrack
• if one adds a soundtrack
• once a soundtrack is added

So the sentence is about the effect of the action, not about the person performing it.

Саундтрек is the direct object of добавить, so it is in the accusative case.

However, because саундтрек is:

• masculine
• inanimate

its accusative singular looks exactly like the nominative singular:

• nominative: саундтрек
• accusative: саундтрек

So the form does not visibly change, but grammatically it is accusative.

Короткометражка means short film or short movie.

It is a fairly common, natural word, but it is somewhat less formal than короткометражный фильм.

So:

• короткометражка = everyday, compact, natural
• короткометражный фильм = more formal or neutral

In conversation and media discussion, короткометражка is very normal.

Literally, звучать means to sound. But Russian, like English, can use sound more broadly.

Here короткометражка звучит иначе suggests that the short film comes across differently, especially because of its audio, mood, tone, or overall impression.

Since the sentence is about adding a soundtrack, звучит is especially appropriate. It connects the film’s new effect to the change in sound.

Иначе means differently / otherwise.

So звучит иначе means:

• sounds different
• comes across differently
• has a different feel

It does not specify exactly how it is different; it just says that the result is not the same as before.

The commas mark the two parts of the construction:

• Стоит только добавить саундтрек,
• как короткометражка звучит иначе.

Russian normally separates these clauses with a comma because как introduces the second clause.

So the punctuation helps show the structure:

• first, the minimal action
• then, the resulting effect

Yes, Russian word order is flexible, but the original order is very natural.

Стоит только добавить саундтрек, как короткометражка звучит иначе sounds smooth and standard.

You may also see variants with slightly different emphasis, but this fixed pattern usually keeps стоит только together near the start.

The main thing to remember is the core frame:

• Стоит только + infinitive, как + clause

If you change the order too much, the sentence may sound less natural or weaken the idiomatic pattern.