  Are you sure abou that? According to Nationalencyklopedin Swedish was melodic during the Viking age:  Source:   No, I'm not sure. I have been in that faith because my Swedish teachers tell so.     It still is quoestion, why Swedish has this tone when Danish and Norvegian doesn't. They still was same language during those ages (practically are today too) and why finlandssvenska lack it too.    The theory goes that after 1809 finlandssvenska remained like Swedish was but because getting French general as new King, rikssvenska started to evolve current direction. And it not tone, but pronounciation too.    But I'm not linguisticist.