Everything is in the title...
'Swinging' because everything is played in uneven eighth notes, and at a brisk pace. “Rondo” because, according to the dictionary, the Rondo is an instrumental piece built on the alternation of a chorus and several verses.
That’s roughly what happens in this quartet (although the chorus undergoes several variations). Add a few percussions, some pizzicato passages, and you get a piece whose atmosphere evokes the jazz of the 1940s.
