This collection uncovers the fascinating past of Tennessee's legendary Music City from true tall tales to larger than life characters and much more.   Perched on the banks of the Cumberland River, Nashville is best known for its role in the civil rights movement, world-class education and, of course, country music. In this unique collection of columns written for The Tennessean, journalist and longtime Tennessee native George Zepp illuminates a less familiar side of the city's history.    Here, readers will learn the secrets of Timothy Demonbreun, one of the city's first residents, who lived with his family in a cliff-top cave; Cortelia Clark, the blind bluesman who continued to perform on street corners after winning a Grammy award; and Nashville's own Cinderella story, which involved legendary radio personality Edgar Bergen and his ventriloquist protegee. Based on questions from readers across the nation, these little-known tales abound with Music City mystery and charm.