Trommen står i øvelokalet ved vinduet.

Because Danish usually marks the definite form by adding an ending to the noun instead of using a separate word like the.

• en tromme = a drum
• trommen = the drum

So trommen means the drum.

In Danish, the definite article is often attached to the end of the noun.

• English: the drum
• Danish: trommen

The same happens later in the sentence:

• øvelokalet = the rehearsal room
• vinduet = the window

So instead of writing a separate the, Danish commonly uses endings like -en or -et.

Danish often uses position verbs where English would simply use is.

Here, står literally means stands. In Danish, that is very natural for many objects that are upright or placed in a standing position.

So:

• Trommen står ... = The drum is/stands ...

Using er is sometimes possible, but står sounds more specific and more idiomatic when talking about where an object is placed.

These are very common location verbs in Danish:

• står = stands, for things seen as upright or placed on a base
• ligger = lies, for things lying flat or resting horizontally
• sidder = sits, for people sitting, but also for things attached/fitted in place

Examples:

• Bogen ligger på bordet. = The book is lying on the table.
• Lampen står på bordet. = The lamp is on the table.
• Billedet sidder på væggen. = The picture is on the wall.

So in this sentence, står suggests the drum is in a standing/upright position.

Øvelokalet is made up of:

• øve = to practice/rehearse
• lokale = room, premises
• -et = the definite ending

So:

• et øvelokale = a rehearsal room / practice room
• øvelokalet = the rehearsal room / the practice room

It is a compound noun, and Danish writes compounds as one word.

Because Danish, like German, normally writes compound nouns as a single word.

So English rehearsal room becomes Danish øvelokale.

More examples:

• musikrum = music room
• klasseværelse = classroom
• soveværelse = bedroom

This is very normal in Danish, so learners need to get used to seeing long nouns written as one unit.

I usually means in and is used for being inside an enclosed space.

So:

• i øvelokalet = in the rehearsal room

That is the natural preposition because a rehearsal room is a room you are inside.

Ved means by, near, or next to.

So:

• ved vinduet = by the window / near the window

This does not mean the drum is inside the window or on top of the window. It means its location is near the window.

Compare:

• i vinduet = in the window, possibly in the window space
• på vinduet = on the window, which usually would not make sense here
• ved vinduet = by the window

Because vindue is a neuter noun in Danish.

Danish nouns are commonly grouped as:

• common gender: often take en in the indefinite form
• neuter gender: take et in the indefinite form

So:

• et vindue = a window
• vinduet = the window

By contrast:

• en tromme = a drum
• trommen = the drum

That is why the endings are different.

The basic structure is:

• Trommen = subject
• står = verb
• i øvelokalet = place
• ved vinduet = more specific place

So the sentence follows a normal Danish main-clause pattern: subject + verb + other elements.

Danish is a V2 language, which means the finite verb is normally in the second position in main clauses.

Then Danish would usually invert the subject and verb, because of the V2 rule.

For example:

• I øvelokalet står trommen ved vinduet.

That still means the same thing, but now the sentence starts with the location. Since I øvelokalet is in first position, står must stay in second position, and trommen comes after it.

Yes, it is grammatically possible, and people would understand it.

But there is a difference in feel:

• Trommen er i øvelokalet ved vinduet focuses more generally on where the drum is.
• Trommen står i øvelokalet ved vinduet sounds more natural if you are describing the physical placement of the drum.

Danish often prefers står / ligger / sidder where English would just use is.

In this sentence, it most naturally describes where the drum is inside the rehearsal room.

So the meaning is:

• The drum is in the rehearsal room,
• and more specifically, it is by the window.

In other words, ved vinduet gives a more exact location for trommen.

A rough guide is something like stor but with the Danish å sound, which is not exactly the same as English or.

A few points:

• å is a rounded vowel, somewhat like the vowel in British law
• r in Danish is softer than in English
• the word is one syllable

If you are learning pronunciation, it is best to hear it from native audio, because Danish vowels can be tricky.

A useful breakdown is:

• Trommen = the subject, the drum
• står = the verb, stands / is positioned
• i øvelokalet = general location, in the rehearsal room
• ved vinduet = more precise location, by the window

So the sentence moves from:

1. the thing being talked about,
2. to its position,
3. to the larger place,
4. to the more exact spot within that place.