[2] In July 1995, he was chosen by Maestro Sir Georg Solti to lead the bass section of the United Nations' orchestra "Musicians of the World."
Barker performed the world premiere of James Yannatos' Bass Concerto (which was written especially for him) with Alea III and subsequently with Collage.
He was the featured soloist at the New England premiere of Gunther Schuller's Bass Concerto, conducted by the composer, with the Boston Pro Arte Chamber Orchestra.
[3] Barker inaugurated the 100th Anniversary Season of the Boston Symphony Orchestra with a solo performance of the Koussevitsky bass concerto, a performance the Boston Globe praised as having possessed "everything that makes great artistry - tone, technical equipment, temperament, repose, a keen sense of rhythm, and fine conception."
[citation needed] Other solo engagements include appearances at Ozawa Hall at Tanglewood, the Festival of Contemporary Music at Tanglewood, Carnegie Recital Hall's "Sweet and Low" series, and recitals at major universities and conferences throughout the world.