Most of the time, I don't listen to any music, as I like listening to the truck's engine. If I do want some music, I might use some random indie pop playlist, or listen to TruckersFM, or for more realism, one of the french highway traffic info radios like Sanef 107.7 or Radio Vinci Autoroutes, which I add to ETS2's live_streams.sii myself. (check out this neat editor!)