Learn Hardcore Norwegian: Forelesningen føles kortere når professoren spiller rytmisk musikk i bakgrunnen. - The lecture feels shorter when the professor plays rhythmic music in the background.

Føles is an -s verb used when something has a quality that is perceived, roughly “feels (to someone).” The subject is the thing being experienced. With a person as the experiencer, you use føler.

Correct here: Forelesningen føles kortere. (The lecture feels shorter.)
With a person: Jeg føler meg trøtt. (I feel tired.)

Could I say blir kortere instead of føles kortere?

Yes, but the meaning shifts:

Føles kortere = seems/feels shorter (subjective impression).
Blir kortere = actually becomes shorter in duration (objective change). In your sentence, we’re talking about perception, so føles is better.

Why is forelesningen in the definite form?

Norwegian often uses the definite when referring to a specific, known item in the context, like “the lecture” you’re attending. You could say En forelesning føles kortere ... to speak generally, but Forelesningen ... points to a particular lecture already known from context.

How is kortere formed, and why not mer kort?

Kortere is the regular comparative of kort (short). For most short adjectives, add -ere (comparative) and -est/-este (superlative):

Positive: kort
Comparative: kortere
Superlative: kortest (indefinite), korteste (definite/with determiner) Using mer kort is unidiomatic; use kortere.

Do we need enn (than) after kortere?

Not here. The når-clause supplies the comparison baseline implicitly (shorter than otherwise). You could make it explicit: kortere enn vanlig, but it isn’t required.

Why når and not da, mens, or hvis?

Når introduces a time clause in the present/habitual sense: “when(ever).”
Da is used for a single past event: Forelesningen føltes kortere da professoren spilte ...
Mens means “while” (two things happening simultaneously), which could also work: ... mens professoren spiller ..., but når is more neutral here.
Hvis means “if” (condition), not appropriate for a pure time relation.

Why is the order når professoren spiller, not når spiller professoren?

In Norwegian subordinate clauses (introduced by når, at, fordi, etc.), the word order is Subject–Verb: når professoren spiller .... Inversion (Verb–Subject) is for main clauses with something fronted.

Can I front the når-clause? What happens to word order then?

Yes:

Når professoren spiller rytmisk musikk i bakgrunnen, føles forelesningen kortere. When you front an adverbial/clause in a main clause, you get inversion (Verb–Subject) in the main clause: føles forelesningen (not forelesningen føles).

Why is there no article before musikk?

Musikk is a mass/uncountable noun in this sense, so no article in the indefinite: ryt*misk musikk. If you specify a particular, known music, use the definite with an adjective: den rytmiske musikken.

Should it be rytmisk or rytmiske?

With an indefinite singular/mass noun, use the base form: rytmisk musikk. You get rytmiske in the definite form or in the plural:

den rytmiske musikken
rytmiske sanger

Could I say i bakgrunn instead of i bakgrunnen?

No. The idiomatic expression is i bakgrunnen (definite). Many set expressions take the definite: i solen, i mørket, i bakgrunnen.

Is på bakgrunn the same as i bakgrunnen?

No:

i bakgrunnen = in the background (spatial/aural setting).
på bakgrunn av = due to/based on.

Is spiller the right verb for music here? What about setter på or har på?

spiller (musikk) = plays music (actively/performing or playing tracks).
setter på musikk = puts on some music (turns it on).
har musikk i bakgrunnen = has music playing in the background. All can fit, with slight nuance differences.

Could we use foreleseren instead of professoren?

Yes, if you mean “the lecturer.” Professoren is a specific academic title; foreleseren refers to the person delivering the lecture regardless of title. Læreren would usually be “the teacher” (school context).

Can I also say Forelesningen kjennes kortere?

Yes. Kjennes and føles often overlap when describing perceived qualities. Føles is slightly more common in general speech; kjennes can sound a bit more tactile or formal, depending on context.

Could I drop i bakgrunnen? Would it change the meaning?

If you say spiller rytmisk musikk, it just states that the professor plays rhythmic music; adding i bakgrunnen highlights that it’s background music (not the main focus). Without it, context has to supply that nuance.

How would this look in the past?

Use da and past tense:

Forelesningen føltes kortere da professoren spilte rytmisk musikk i bakgrunnen.

Is it okay to use føles som here?

Here you don’t need som because the complement is an adjective (kortere). Use føles som when followed by a noun phrase or clause: Det føles som ferie, Det føles som om tiden går fortere.

Any quick pronunciation tips for tricky parts?

føles: ø like French “deux”; roughly [føː-]. The final -s is pronounced.
rytmisk: y like German “ü” (short), and tm is articulated clearly.
bakgrunnen: double nn gives a longer n; stress is on bak. Natural speech links words: professoren spiller flows without a pause.

Is there a Nynorsk equivalent?

Yes: Førelesinga kjennest kortare når professoren spelar rytmisk musikk i bakgrunnen. (Common Nynorsk choices: førelesinga, kjennest, spelar.)