Well most of the music I've mentioned so far are amongst what I would consider the "core" of the "classical music repertoire" today.
I know of Sibelius' Violin Concerto. I don't myself prefer some music in regards to other - there's of course some music I listen to rarely than others, but in my experience it's mostly a matter of personal mood which sets the "musical requirements".
Carl Nielsen has written a "fantasy" for oboe and piano, I don't know if it's the one you're refering to? I've both heard and played the (wood)wind quintet.
Kuhlau has also written the music for the Danish "goldenage" play "Elverhøj" ("The Elf Mound" - roughly translated) which is amongst the highly treasured stagepiece of that era and which also includes one of the two Danish "national anthems" - this one being the royal anthem - as opposed to the more widely regarded "Det er et yndigt land" ("A lovely land is ours") which is the one used at international sporting events. He's also been instrumental in introducing some of the old Danish folktunes - of which several are featured in "Elverhøj". - And naturally, as a hornplayer there's also his concertpiece for two horns and orchestra.
Hartman is probably one of the least known composers abroad, having contributed in no small part to the Danish "sangskat" (treasure of songs - direct translation), a word describing the songs written mainly in the middle of the 19th century but which also streches back to the early rennaisance and the earlist of folktunes.