Donald Mills, Harry Mills, Herbert Mills, and John Mills: The Mills Brothers perform Swing It, Sister in the 1934 film Strictly Dynamite.
The Mills Brothers, sometimes billed as The Four Mills Brothers, and originally known as The Four Kings of Harmony, were an American jazz and pop vocal quartet of the 20th century who made more than 2,000 recordings that combined sold more than 50 million copies, and garnered at least three dozen gold records. The Mills Brothers were inducted into The Vocal Group Hall of Fame in 1998.
Note the excellent mouth trumpet action, a jazz-era vocal technique that imitates the sound of a trumpet. Try it!
Related watching: Ella Fitzgerald scat singing One Note Samba, Dizzy Gillespie performing Salt Peanuts, and The Music Instinct: Taylor and Bobby McFerrin.