“Keep cool … but care” has been a hipster mantra since Thomas Pynchon coined it, but politics, protest, social conscience, the urge to heal are sometimes an opportunistic afterthought in popular music. Isn’t its real logic hedonistic? Some bands walk the line confidently. Glasgow dwellers Belle and Sebastian released their masterpiece The Boy With the Arab Strap in 1998, which makes them veterans, who’ve also managed to straddle the other critical line between indie cred and a fulsome, radio-friendly sound.