Those minstrels very likely did improvise some sort of song, but very unlikely it was a ballad. It's also quite likely that the ballad form spread from France to Scandinavia in about the 13th century. Were there any 'Vikings' in the 13th century? We tend to think about 10th century and earlier for Vikings. Is the Gilbert book a historical fiction? Certainly looks that way. You use the phrase 'big ballads'. Very few of OUR big ballads can be traced back beyond 1500. There is also very little evidence for the Danish ballads before that date, though some refer to events in the 13th century. Methinks you're pulling our legs, Al.