For people who are actually interested in how viking music might have sounded, “Drømde mik en drøm i nat" (/I dreamt a dream last night) is the earliest music (and lyrics) known in Scandinavia preserved on the last page of the (~1200-1300) Codex Runicus as rune notes.
The song and melody is still known and used today in most of Scandinavia, as a sort of folk-standard. This version, deceivingly slow in the beginning, is presented as close to the original sound of the years 900-1000 as historians think they can come.
This song might have survived because it was a gigantic hit, like the viking’s very own “Billie Jean”. A total pop slayer that stayed around long enough for music notes to be invented.
The more you know.