SEATAC, Washington — Background music is no longer an afterthought at many airports, which are hiring local musicians and carefully curating playlists to help lighten travelers’ moods.

Low mileage and quirky, incongruous decals are this Chevy sedan’s calling cards.

But Barry McPhillips, the head of international creative for Mood Media, which provides music for airports and other public spaces, said technology is enabling background music to be less generic and ...