"When we were in our mothers’ wombs, God had decided what he wanted us to be,” says Beverly “Guitar” Watkins, “and he wanted me to be a musician.” Upon seeing the 74-year-old Watkins play fiery guitar solos—often with her guitar slung behind her head—over her hard-edged mix of blues and early rock and roll, it is hard to disagree with the Lord’s designation. Even after over 50 years in the music business, Watkins still sees music as a vocation rather than a job. “Blues is a feeling,” says Wat...