Learn Hardcore Swedish: På konserten vill jag sjunga med. - At the concert I want to sing along.

So: På konserten vill jag sjunga med is correct.
På konserten jag vill sjunga med is wrong because the finite verb is no longer in second position.

In more neutral order (subject first), you could also say: Jag vill sjunga med på konserten.

Can I also say Jag vill sjunga med på konserten? Is it different in meaning?

Yes, Jag vill sjunga med på konserten is completely correct.

The meaning is the same; the difference is mostly in emphasis and style:

Jag vill sjunga med på konserten.
– Neutral, everyday word order (subject first).
På konserten vill jag sjunga med.
– Slight emphasis on at the concert (as opposed to somewhere else).
– Often used in spoken Swedish when you want to highlight the place or connect to something just mentioned (e.g. “What about the concert?” – “På konserten vill jag sjunga med.”).

Why is it sjunga and not sjunger?

After a modal verb in Swedish, you normally use the infinitive without att.

Vill is a modal verb (like kan, ska, måste, bör), so the next verb stays in the infinitive:

Jag vill sjunga. – I want to sing.
Not: Jag vill sjunger. (incorrect)

Compare:

Jag kan sjunga. – I can sing.
Jag ska sjunga. – I will/am going to sing.
Jag måste sjunga. – I must sing.

So vill sjunga is the correct structure.

What exactly does vill mean here? How is it different from ska or kommer att?

Vill mainly expresses desire / wish:

Jag vill sjunga med.
= I want to sing along.

Rough comparison:

vill – want to
- Focus: desire/intention from the speaker.
ska – shall / going to (often more planned or decided)
- Jag ska sjunga på konserten. = I am going to sing at the concert (it’s arranged).
kommer att – will (more neutral, future event)
- Jag kommer att sjunga på konserten. = I will sing at the concert (prediction/plan).

In your sentence, vill is about what you want to do at the concert.

What does sjunga med literally mean, and how is it different from just sjunga?

Literally, sjunga med is “to sing with”, but idiomatically it means “to sing along”.

sjunga – to sing (in general)
sjunga med – to sing along (with someone / with the music)

Example contrasts:

På konserten vill jag sjunga.
= At the concert I want to sing (maybe perform myself, sing a solo, etc.).
På konserten vill jag sjunga med.
= At the concert I want to join in and sing along (with the band, with the audience, etc.).

So med here is part of a particle verb (sjunga med) with its own meaning.

Do I have to include med? How does the meaning change if I leave it out?

You don’t have to include med grammatically, but it changes the meaning:

På konserten vill jag sjunga.
= I want to sing at the concert (you might be on stage performing).
På konserten vill jag sjunga med.
= I want to sing along (join others who are singing, or sing along with the music).

So med gives the specific idea of joining in rather than simply singing.

Why is it på konserten and not i konserten or vid konserten?

Swedish often uses på for events, activities, and certain places where English would say at:

på konserten – at the concert
på festen – at the party
på lektionen – in/at the lesson/class
på bio – at the movies
på jobbet – at work

I konserten would sound strange; it would literally suggest inside the concert and is not idiomatic for attending it.

Vid konserten (by/near the concert) would only be used in very specific contexts about physical location nearby, not about being an attendee.

So på konserten is the natural way to say “at the concert”.

Why is it konserten (with -en) and not en konsert?

Konserten is the definite form: “the concert”.
En konsert is the indefinite form: “a concert”.

På konserten vill jag sjunga med.
= At the concert I want to sing along (a specific concert that both speakers know about).
På en konsert vill jag sjunga med.
= At a concert I want to sing along (any concert, in general).

So the -en ending marks definiteness: konsert → konserten.

Is På konserten vill jag sjunga med formal, informal, or neutral?

It is neutral, standard Swedish.

You can use it in spoken language and in informal writing (messages, emails).
It’s also fine in more formal contexts if the topic itself is informal (talking about what you want to do at a concert).

There are no slang words or very formal expressions in the sentence.

Where would I put inte if I want to say “I don’t want to sing along at the concert”?

Negation inte normally comes after the finite verb in main clauses.

So:

På konserten vill jag inte sjunga med.
= At the concert I don’t want to sing along.

Neutral order:

Jag vill inte sjunga med på konserten.

Structure in the neutral version:

Jag (subject)
vill (finite verb)
inte (negation)
sjunga med (infinitive verb phrase)
på konserten (place adverbial)