“It’s a mighty thin line between certain kinds of country and classic rhythm and blues. Look at John Hiatt. Or Bonnie Raitt. Or Chris Webster. The singer/songwriter from Davis, California (known to many as one of the dynamic singers in the NorCal eclectic septet Mumbo Gumbo) blends the two styles in a way that has distanced her from the country mainstream but endeared her to fans of soulful singing. Webster’s is an authoritative voice that manages to make existential angst, romantic confusion and spiritual longing sound uncommonly appealing. Each note she sings conveys a probing, acute sensitivity to the little...