Morton Feldman is not one of my favorite composers. His work can be described as the musical equivalent of watching clouds go by for hours and hours. However, in his opus, two particular pieces stand out: the aria Only and his work named for Rothko Chapel in Houston (seen on the left.)
Feldman is not particularily lyrical, but at least his music is not painful on the ears like Boulez and Stockhausen. He deserves at least one listen.
More information about Feldman can be found here