Learn Hardcore Indonesian: Di film misteri itu, suara langkah di lorong begitu jernih sampai saya ikut tegang. - In that mystery film, the sound of footsteps in the corridor is so clear that I feel tense too.

Di film misteri itu ≈ “in that mystery movie / in the mystery film.”
You can say dalam film misteri itu; it sounds a bit more formal or bookish, and often emphasizes “within the content of the film.”
Pada is rarely used with film in this sense; pada is more for abstract things (e.g. pada kesempatan itu, “on that occasion”).

So di film misteri itu is the most natural everyday way to say “in that mystery film.”

Why do we have itu at the end of film misteri itu? Is it “that” or “the”?

Itu literally means that, but it often functions like the when you’re talking about something specific that both speaker and listener know.

film misteri itu = “that mystery film” / “the mystery film (we both know which one).”

Without itu, film misteri would sound more like “a mystery film (in general).”
With itu, it’s clear the speaker is referring to a particular movie.

Why is it suara langkah and not suara langkah kaki? Is something omitted?

Literally:

suara = sound
langkah = step
langkah kaki = (foot)step

Suara langkah already naturally means the sound of footsteps. Indonesians frequently drop kaki here because it’s understood from context:

suara langkah (common and natural)
suara langkah kaki (also correct, a bit more explicit)

So nothing is “missing”; suara langkah on its own is normal Indonesian.

What does lorong mean exactly? Is it “hall,” “hallway,” or “corridor”?

Lorong means a narrow passage between walls or buildings. In this context, it’s best translated as:

hallway or corridor inside a building.

It’s not used for a big open hall (like a hotel lobby). For a big hall, you’d use words like aula or balai, not lorong.

What does begitu jernih mean? Why not just sangat jelas?

Breakdown:

begitu = so / that (to such an extent)
jernih = clear (often used for sounds, water, images)

So begitu jernih ≈ so clear or so crisp.

You could say sangat jelas (very clear), but:

jernih emphasizes clarity in a sensory way (sound quality, water purity, image sharpness).
jelas is more general “clear” (also in the sense of “understandable”).

In a sound-related context like this, jernih is a bit more vivid and descriptive than jelas.
Begitu jernih also sets up the sampai… clause: so clear that…

How does the structure begitu ... sampai ... work in this sentence?

The pattern is:

begitu + adjective + sampai + result clause

Meaning: so [adjective] that [result].

In the sentence:

begitu jernih = so clear
sampai saya ikut tegang = that I also became tense

So the full idea is:
“(It was) so clear that I ended up feeling tense too.”

What does ikut mean in sampai saya ikut tegang? It usually means “to follow,” right?

Yes, the basic meaning of ikut is to follow / to join. But in colloquial and standard Indonesian, ikut is also used to mean “also / as well” (joining in a state or action).

In sampai saya ikut tegang:

ikut = to also experience the same thing / to get drawn into the emotion
tegang = tense

So saya ikut tegang means: I also got tense / I ended up tense too, carried along by the atmosphere of the movie.

What kind of “tense” is tegang? Is it fear, nervousness, or suspense?

Tegang usually describes:

physical or emotional tension,
a suspenseful, on-edge feeling.

It does not directly mean “afraid” (takut) or “nervous before performing” (gugup). In a movie context:

tegang ≈ “on the edge of my seat / in suspense.”

So saya ikut tegang is more like “I got really tense and on edge,” not simply “I was scared.”

Could we change the word order, for example: Suara langkah di lorong di film misteri itu begitu jernih…?

You can move phrases around, but some orders sound more natural. The original:

Di film misteri itu, suara langkah di lorong begitu jernih sampai saya ikut tegang.

This:

starts with Di film misteri itu to set the scene,
then presents the main subject suara langkah di lorong.

If you say:

Suara langkah di lorong di film misteri itu begitu jernih…

it’s understandable, but it sounds a bit heavier and less smooth.
Another natural variant would be:

Suara langkah di lorong dalam film misteri itu begitu jernih…

Still, the original order (scene-setting phrase first) is very typical and stylistically good Indonesian.

Why is there a comma after Di film misteri itu? Is it required?

The comma is stylistic but very common.

Di film misteri itu is a fronted adverbial phrase (a setting: “In that mystery movie”).
Indonesian often uses a comma after such a phrase, similar to English:
In that mystery movie, the sound of footsteps…

You’ll also see it written without a comma in informal writing, but with the comma is considered clearer and more standard, especially in careful or published text.

Is saya here formal? Could I use aku instead?

Yes, saya is the polite / neutral first-person pronoun, appropriate in:

narration,
formal writing,
when you don’t know your audience well.

You could say:

…sampai aku ikut tegang.

That sounds more casual/intimate, typical in:

informal speech,
dialogues between close friends,
some casual writing (blogs, chats, etc.).

Meaning doesn’t change; it’s just a shift in formality and tone.