Gaylon Horton, 42, who founded Music Solutions to negotiate use of recording artists' songs as soundtracks for television and motion pictures. Before he created his pioneering company in 1984, Horton was head of the Pop Music publishing division for the Welk Music Group. He had also worked as a disc jockey, winning the designation of "Air Personality of the Year" from Billboard magazine. Horton was a past president of the California Copyright Conference and chairman of the National Music Publishers Forum. A popular university guest lecturer about music publishing, he created and taught a UCLA class on film music supervision based on his work with Music Solutions. On Saturday in Sherman Oaks of leukemia.