Carl Nielsen's highly personal amalgam of traditional and modern styles is evident in his comic opera Maskarade, which is a perennial hit in Denmark, though scarcely known to the rest of the world.  It is a supremely funny and entertaining work, based on a classic of Scandinavian literature, Ludvik Holberg's 1724 comedy of the same name.  (Holberg, claimed both by Danes and Norwegians as one of their own, was memorialized by Edvard Grieg in his popular Holberg Suite.)

The plot of the opera has been aptly summarized by Steven Ledbetter, former program annotator of the Boston Symphony Orchestra:

Two fathers have arranged for the son of one to marry the daughter of the other.  But their children (who have never set eyes on each other) have other plans.  Both of them have been out celebrating the carnival season in the required costume and mask, and both have fallen in love with a stranger.  The two fathers are distressed:  the two young people are steadfast in their determination not to bow to the paternal will.  Of course, as the audience will have guessed from the first scene, they have actually managed to fall in love with the mates proposed by their parents, though it takes a good deal of confusion and much mistaken identity on the part of the maskers to bring about this resolution.

In addition to mistaken identities, the masquerade obliterates all social differences:  you don't know who is a nobleman and who is a servant.  And—even more importantly for an opera—the masquerade allows for a lot of song and dance, which is what the overture evokes.  The melodies are simple and catchy, though they are worked out with a great deal of sophistication, with busy contrapuntal activity and an extremely colorful orchestral writing.  One may distinguish three sections:  the overture opens and closes with a theme announcing the masquerade (it is also used later in the opera); in between, the dancers take center stage, their performance starting out tender and lyrical, to become furioso towards the end.