Translation:They bought the violin with stolen money.
In principle you can, but it's more common and sounds more idiomatic if you say för.
Different verbs take different prepositions: Jag betalar med pengar 'I pay with money' but Jag köper för pengar- lit. 'I buy for money'.
Swedish sees it like this: for betala, the money is an 'instrument' – I'm fulfilling the action 'to pay' by using money.
For köpa, we see that as an exchange. You've got this idea in English when you say 'to exchange something for something'. Or in expressions like 'I bought it for $10'.
So way back in the first lesson on verbs this statement was made: We do not conjugate verbs based on who is performing the action. Ever! Not for the present tense, not for any tense! Not for any verb! Ever! We promise! 100% guaranteed! So if I understand this correctly, this is true for all forms of a verb except for the past participle which is inflected for the object that is acted upon. In this sense the past participle acts as an adjective and is inflected as such. Am I understanding this correctly?
Yes. Very good summary, actually. I might add that linguists have been arguing about what exactly participles constitute for ages now - are they adjectives? Verbs? Something else? If you look stulen up in three different dictionaries, you might actually find it listed in at least two different manners. I personally just think of it as an adjective - makes life easier. :)
Ah, well then, my Anki Swedish Adjective deck is suddenly going to become much larger. :)
I've noticed when working on this course that the participles are so much more "adjective-ish" in Swedish than in English, so it's probably helpful to think of Swedish participles as adjectives. Rule of thumb: don't use a participle if you don't mean it as an adjective :)
(later edit: or an adverb!)
If the course was for Spanish speakers it could be easier to understand the way past participles work, because they do it the same way in Spanish. The easiness of English sometimes make it hard to learn other languages. One get lost in translation very often, more than one thought in the first instance
In French "payer les violons" and in Swedish "betala för fiolerna" is an expression. Who often means that you kind of have ended up with paying for the whole dinner party instead of only yourself. Often in a negative way. Like a friend who can't pay and you say:"Jaha, då är det väl jag som får stå för fiolerna".