SILVER SPRING, MD. - Mike Auldridge, a bluegrass musician whose broad knowledge of many musical forms helped redefine and modernize the steel guitar known as the Dobro, died Saturday, a day before his 74th birthday.

He had prostate cancer, said a daughter, Michele Auldridge.

Auldridge was a founding member of the Washington-based bluegrass group the Seldom Scene and, in a career spanning six decades, he recorded with Linda Ronstadt, Lyle Lovett and Emmylou Harris, among others.

He was renowned for his mastery of the Dobro, a guitar with a metal resonator instead of a sound hole. In addition to the Dobro, Auldridge was also accomplished on the lap steel and pedal steel guitars.