It's been two decades since Dar Williams' debut, but time has made her music no less lithe, energetic or open-hearted. Though Williams came up in the Boston folk scene, she's always been drawn to rock and pop. That's the spark at the heart of her songs, which range from poignant sketches of Bible camp kids ("Teen for God") to stories about Stanley Milgram's notorious electric-shock obedience experiment ("Buzzer"). Last year's In the Time of Gods is arguably her most sophisticated release musically, full of warm and smoky but understated texture and moody adult pop languor. Angel Snow opens.