Avant-garde composer and conductor who was celebrated among New Yorkers for decades as a mysterious street performer who dressed as a Viking, and who later won acclaim in Europe for his music. He was 83. From the late '40s to the early '70s, Hardin, who was blind, stood at attention on Sixth Avenue and 54th Street, dressed in a homemade robe, sandals, cape and a horned Viking helmet. Unbeknownst to many, Hardin had recorded his jazz-flavored compositions on the CBS, Prestige, Epic, Angel and Mars labels. One of his songs, "All is Loneliness," became a hit recorded by Janis Joplin. Hardin also wrote music for radio and television commercials. Celebrated by Beat Generation poets and followers, one of his recordings, "Moondog Symphony," was regularly played by Alan Freed, the pioneering rock-and-roll disk jockey. In 1989, Hardin, who had been living in Europe, was invited back to the United States to conduct the Brooklyn Philharmonic Chamber Orchestra.