My store is pretty lax about listening to music, at least in the backroom. We can play music through our phone speakers or with one earphone in but no one ever says anything if both are in. We also have several people blasting music through big speakers in the backroom e.g. Girl in receiving playing pop music, guy at the baler playing death metal, guy in electronics stockroom playing classic rock, and janitorial crew playing Mexican love songs. One backroom team member always plays uncensored comedy albums through his phone speaker at full volume. No one seems to mind. The floor is usually limited to one earphone in.