Since we're discussing existing civs, I'll give my thoughts on Norway's music.
I am frankly somewhat disappointed with Norway's portrayal in general. Other civs have attributes that span much more of their history, such as America with its P-51 Mustang and Film Studio despite being led by Teddy Roosevelt, Germany with its U-Boat despite being led by Frederick Barbarossa, and Japan with its Electronics Factory despite being led by Hojo Tokimune. Norway, however, gives an impression that it stopped existing as a nation and concept after the Viking Age. I realise that Norway is supposed to be carrying the mantle of the "Viking" civ this time around after Denmark and the Vikings themselves, but still, I wish it didn't have to completely exclude any representation of post-Viking Norway. (which is why I hope that any potential rework would include something that modern Norway could identify with)
I wrote this to give some background to my choices if Norway were to be given themes with multiple pieces, like the civs of both expansions have.
Gjendines bådnlåt, Norway's current theme, already covers the folk/rural/traditional aspect of Norwegian music, so I personally feel like any additional melody would have to be post-1814, representing the era in which Norwegians began to focus on rebuilding a unique culture, to distance themselves from the Danes and Swedes - an effort which would shape the Norwegian people's view on their country, and their relationship with it to this very day, making it a very important chapter of our history. So, for this reason my suggestions/ideas are:
Norge, mitt Norge -
Norway, My Norway
Originally a poem written in 1901, four years before Norway would again become an independent country, its lyrics depict Norway as "sleeping," illustrating Norwegian attempts to "wake up" the country by reviving Norwegian culture, and also describes Norwegian nature in detail - an aspect of Norway which became central in rebooting Norwegian cultural identity.
Nordmannen -
The Norwegian
Popularly known as
Mellom bakkar og berg ("Between Hills and Mountains"), this was originally a poem published in 1863, which focuses on and highlights the Norwegian's shrewdness in settling and improving his homeland. Worth noting is that this was written by
Ivar Aasen, who created one of the written forms of Norwegian still used today, in a time where the status and future of a Norwegian written language was hotly debated, after Danish had been the sole official language for the past 400 years or so.
I Dovregubbens hall -
In The Hall of the Mountain King
Perhaps Norway's most well-known orchestral composition, composed by Edvard Grieg in 1875 for
Peer Gynt, one of Henrik Ibsen's plays. Both Grieg and Ibsen were very important for Norway's cultural revival, and so a combination of their efforts would fit nicely. However, featuring it in the game would be quite ironic, as Grieg himself said that it was so "ultra-Norwegian" that he couldn't bear to hear it. Anyway, if so, it'd obviously have to be the finale of a reworked Norwegian theme.
I was also going to suggest some melodies which could work as more ambient music, but this reply is already too long. I'll do so some other time, in another reply.