At 17, Isac Elliot of Finland is already a pop veteran. He is starting to take a larger role in steering his own career.

In early July, Alma Miettinen dropped her first song, “Karma,” just to see what would happen. Less than two months later, “Karma” became the second-most streamed Finnish song of the 2010s on Spotify, right after “Hollywood Hills” by Sunrise Avenue.