Any of Emmylou Harris’ albums are worth having, but Elite Hotel, Pieces Of The Sky, Cowgirl’s Prayer, Wrecking Ball and Red Dirt girl are almost essential. Cowgirl’s Prayer has one of the most beautiful, haunting songs on it, Prayer In Open D, which can practically have me in tears. It’s the song I want played at my funeral.
Pieces Of The Sky has Boulder To Birmingham on it, a song she wrote about her relationship with Gram Parsons, and another beautiful song.
Patty Griffin can sort of be classed as country, but covers rock, folk, jazz, sometimes on the same album. She works with Emmylou quite often as well. Flaming Red, her second album, has the most contrast, and is well worth getting.
Gillian Welsh as mentioned is amazingly good, more earthy early twentieth century style music, sort of dust bowl era.