That tight four-part harmony is unmistakable. And it's been around for a long time.
Barbershop quartets trace their roots back to the late 19th century, when African-Americans would gather in barbershops and on street corners to sing (it was called "cracking a chord"). The term "barbershop" was originally a put-down, but the 1910 song "Play That Barbershop Chord" put that to rest; by then, close-sung harmony was a national hit.
By the end of the World War II, women decided to form their own society for barbershop-style singing: Sweet Adelines International. The organization grew quickly, and today boasts nearly 23,000 members in more than 500 choruses. Peggy Gram joined as a teenager 50 years ago, and has served as the organization's president.
On the occasion of Sweet Adelines' 70th anniversary, Gram spoke with NPR's Wade Goodwyn about the history of women in harmony — and was joined in the studio by current-day female foursome Lustre Quartet, who provided some live demonstration of their craft. Hear the conversation, and the music, at the audio link.