A 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 to amaze 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 "Tiger Rag" an...