that coworker playing nordic music on spotify without headphones so everyone can "concentrate"... (his own words...)

Do it man, for all of us. Tell him on his face, once you show us the way we will start the moment in our respective places too

Two different approaches:
1. Put an axe through his skull (might end up in trouble depending on where you live)
2. Put some K-Pop on speaker and louder than him. Ensue a terrible musical contest.

The first one will be better for your colleagues though.

@Jilano the first one is perfect, now to find a axe

@Jilano the second idea would be asking for trouble, the guy might like it and play it for even more peace and motivation on his premium high quality speakers that you always dreamt of buying

I think you should just hit him on the face with your keyboard, like in the movie wanted, would be a scenario