Gad vide, om koret øver den samme melodi igen i aften.

Gad vide is a fixed Danish expression meaning I wonder.

It is not usually translated word-for-word. In this sentence, it introduces a thought or speculation:

Gad vide, om ... = I wonder if / I wonder whether ...

So the important thing for a learner is to treat gad vide as a set phrase.

Danish often uses gad vide without an explicit subject when it means I wonder.

So:

Gad vide, om koret øver ...
and
Jeg gad vide, om koret øver ...

both make sense.

The version without jeg is very common and idiomatic. It sounds like a natural way to introduce a thought.

Here om means whether / if and introduces an indirect yes-no question.

The speaker is wondering whether the choir is rehearsing...

Compare:

• Jeg ved, at han kommer. = I know that he is coming.
• Jeg spørger, om han kommer. = I ask whether / if he is coming.

So after gad vide, om is the normal choice when the speaker is wondering about something with a yes/no answer.

Because after om, you have a subordinate clause, and Danish subordinate clauses normally keep subject + verb order.

So:

• Direct question: Øver koret i aften? = Is the choir rehearsing tonight?
• Indirect question: ... om koret øver i aften = ... whether the choir is rehearsing tonight

This is a very common pattern in Danish:

• direct question = often verb first
• indirect question = subject before verb

Koret means the choir.

It comes from the noun kor, which is a neuter noun:

• et kor = a choir
• koret = the choir

The ending -et is the normal definite singular ending for many neuter nouns.

Øver is the present tense of at øve.

• at øve = to practise / to rehearse
• øver = practises / rehearses

With a choir, English will often translate it as rehearses rather than practises, because that sounds more natural in context.

Also, Danish verbs do not change for person:

• jeg øver
• du øver
• koret øver

The form stays the same.

Because Danish often uses the present tense for something happening in the near future, especially when a time expression makes the meaning clear.

So:

Koret øver i aften
literally uses present tense, but in English it may be translated as:

• The choir is rehearsing tonight
• The choir rehearses tonight
• The choir will rehearse tonight

All of these can fit, depending on context.

Den samme melodi means the same melody.

Here is the structure:

• den = the / that, agreeing with a common-gender singular noun
• samme = same
• melodi = melody

Since melodi is a common-gender noun, Danish uses den samme before it.

If the noun were neuter, you would use det samme instead.

Because in Danish, when a noun has a word like den plus an adjective-like word before it, the noun itself is usually left in its basic form, not the suffixed definite form.

So Danish says:

• den samme melodi
• den røde bil
• det store hus

not:

• den samme melodien
• den røde bilen
• det store huset

This is a very important Danish pattern.

Igen means again, and here it modifies the action øver.

So the idea is that the choir is rehearsing that melody again.

In other words:

• øver ... igen = rehearses ... again

It does not describe melody itself; it describes the repeating of the action.

That is a very natural Danish word order.

The basic structure here is:

koret + øver + den samme melodi + igen + i aften

So you get:

• subject: koret
• verb: øver
• object: den samme melodi
• adverb: igen
• time expression: i aften

This order sounds neutral and normal.
You can move adverbs around in Danish for emphasis, but this version is the most straightforward.

It can match either tonight or this evening in English, depending on context.

In many everyday translations, i aften is simply rendered as tonight.

So:

igen i aften = again tonight

That is the most natural English equivalent in this sentence.