It’s not unusual for A.A. Williams to see a few tears drop in the darkness. Playing to a congregation scattered amongst the pews of Glasgow’s historic Mackintosh Church at sunset on the second Saturday in November, there is an air of uncertainty. Many of the punters gathered for the city’s Great Western festival – a genre-hopping showcase for everyone from Russian protest-punks Pussy Riot to Bristol techno-metallers SCALPING – seem to be indulging in the London singer-songwriter’s ethereal sound for the first time. Dabbing their eyes in the long shadows, however, the real devotees in attendance are enjoying a near-religious experience. “I’m all for it,” she smiles in the electric afterglow. “A lot of people get very emotional at my shows; it’s quite common to see fans,...