An astonishing vocal group that grew into one of the longest-lasting oldies acts in American popular music, the Mills Brothers quickly moved from novelty wonders to pop successes and continued amazing audiences for decades. Originally billed as "Four Boys and a Guitar," the group's early records came complete with a note assuring listeners that the only musical instrument they were hearing was a guitar. The caution was understandable, since the Mills Brothers were so proficient at re-creating trumpets, trombones, and saxophones with only their voices that early singles like "T...