Morale bonus inconsistency [git b85c4a930b]

I have both a mp3 player [on] and a car stereo [on] 4 tiles away, morale is +20. When I turn off the mp3 player, music bonus becomes +30.

i always chocked this up to the mp3 player uses earbuds while the car is stereo sound, earbuds can get uncomfortable and the sound quality isn’t always the best.