Rundgången börjar under soundchecken.

Because rundgång is an en-word in Swedish, and -en is the definite singular ending.

• rundgång = feedback / audio feedback
• rundgången = the feedback

Swedish usually adds the definite article to the end of the noun instead of using a separate word like English the.

Here, rundgång means audio feedback: the loud squealing, humming, or howling sound you get when a microphone picks up sound from a speaker and re-amplifies it.

So Rundgången börjar means the feedback starts or the audio feedback begins.

For the same reason: soundcheck is being treated as an en-word, and -en makes it definite singular.

• en soundcheck = a soundcheck
• soundchecken = the soundcheck

Swedish often does this with borrowed English words too.

Because Swedish usually marks definiteness by attaching it to the noun itself.

So instead of saying:

• the feedback
• the soundcheck

Swedish says:

• rundgången
• soundchecken

This is one of the biggest differences from English noun structure.

Here under means during.

So:

• under soundchecken = during the soundcheck

Even though English under often means physically beneath something, Swedish under can also mean during in time expressions.

Under soundchecken emphasizes during the time of the soundcheck.

På soundchecken would sound more like at the soundcheck or at the soundcheck event/location.

So if the idea is that the feedback starts while the soundcheck is happening, under soundchecken is the natural choice.

Börjar is the present tense of börja (to begin / to start).

• börja = to start
• börjar = starts / is starting

In this sentence, it simply means starts or begins.

Because Swedish normally follows the V2 rule in main clauses: the finite verb usually comes in the second position.

Here the order is:

1. Rundgången = subject
2. börjar = finite verb
3. under soundchecken = adverbial phrase

That is a very standard Swedish sentence pattern.

Yes. For example:

Under soundchecken börjar rundgången.

This is also correct. Swedish still keeps the finite verb in second position:

1. Under soundchecken
2. börjar
3. rundgången

Changing the order can shift the emphasis slightly. Starting with Under soundchecken puts more focus on the time.

Yes, soundcheck is commonly used in Swedish, especially in music and live-performance contexts.

A more Swedish-sounding alternative exists in some contexts, but soundcheck is very natural and widely understood. Loanwords from English are common in technical, music, and media language.

It would be:

Rundgång börjar under en soundcheck.

That means something like feedback starts during a soundcheck in a more general sense, not referring to one specific feedback noise and one specific soundcheck.

Compare:

• Rundgången börjar under soundchecken. = the feedback starts during the soundcheck
• Rundgång börjar under en soundcheck. = feedback starts during a soundcheck

A rough guide is:

RUND-gong-en

But remember:

• the u in rund is not exactly like English u
• the å in gång is a long vowel, somewhat like the vowel in British law, though not identical
• the ng is pronounced like the sound in English sing

A rough learner-friendly approximation is:

RUN-d-gawng-en

Not perfect, but close enough to help at first.