A group of two men and two women, calling themselves "The Martins" sing and dance to the title song, interpolated with snatches of other tunes in this very pleasant soundie.
Soundies were short films, about three minutes in length. The were meant to be played on a machine called a Mills Panoram, a video jukebox that was typically to be found in bars, lounges, and similar venues. You put a dime in and got a performance from the ten on the machine. The movies would be changed weekly, and from 1940 through 1946, Mills and other companies produced more than two thousand soundies.
I don't mean they're all wearing the same dress: just the two women.