John Prine wrote country-folk songs with an unpretentious, aw-heck demeanor that belied their astonishing gravity and power. “He sings rather quietly, and his guitar work is good, but he doesn’t show off,” Roger Ebert wrote of an early Prine show in 1970. “After a song or two, even the drunks in the room begin to listen to his lyrics. And then he has you.”