It might seem ironic that Swedish musicians are unhappy with their participation in Swedish-born Spotify. But it makes sense that if any national group of artists would take action related to Spotify payouts, it would be in Sweden, where streaming music has become rampantly popular. Spotify reportedly accounts for 70 percent of Swedish music sales, with 10 percent of the population subscribing to the paid service.
The musician argument is less with Spotify than with labels, and how Spotify revenue is shared with artists by those labels. When Spotify income is treated like album-sale income (physical or download), artists share the money according to a royalty split, typically 10 percent. Licensing revenue, by contrast, is often set as a 50/50 split in artist contracts, and the Swedish complaints assert that Spotify distribution of music tracks should be a licensing scenario. The musicians union involved in this controversy is threatening action to remove artist repertoire from Spotify.
This Swedish page can be translated for quotes by the union head. The Guardian has an English write-up here.