The so-called "Goldberg" Variations by Johann Sebastian Bach, BWV988, is a work for harpsichord, consisting of an aria with 30 variations, concluding with the repetition of the opening aria. The form of each variation follows that of the the aria: two sections of equal length, each repeated. The relationship between these two sections is that of antecedent and consequent, and the two halves of each section are similarly related.

The last variation is a quodlibet: a musical joke that quotes tunes from popular or folk songs, and treats them contrapuntally. This variation quotes two different songs:

          Ich bin so lang nicht bey dir g'west. / Ruck her, ruck her, ruck her! / Mit einem tumpfen 
          Flederwisch, / D'rueber her, d'rueber her, d'rueber her!
[It has been so long since I was 
          with you. / Bounce over here, bounce over here, bounce over here! / With a casual   
          fluttering whisk, / Fly over here, fly over here, fly over here!]

          Kraut und Rueben haben mich vertrieben. / Haett' meine Mutter Fleisch gekocht, / Waer' 
          ich laenger blieben.
[Cabbage and turnips have driven me away. / If my mother had   
          cooked meat, / I would have stayed longer.]

Bach's counterpoint here is wonderfully clever, and extremely dense. Most of the snatches of quoted melody are in the inner voices. The only quoted snatches that stand out, are those in the top voice of the first section. These are the first lines of the two songs, one right after the other. They come from two entirely different songs, but they are presented here as if they were antecedent and consequent, like everything else in the work:

          It has been so long since I was with you. Cabbage and turnips have driven me away.

Some commentators and critics (not all) ask the obvious question: Does this juxtaposition mean something? The consensus is a rather clever idea, based on the fact that Kraut und Rueben [cabbage and turnips], in the slang of Bach's time, meant "a hodgepodge" or "a mixed bag." The idea is, that this refers to the repetition of the aria after this variation -- that the quodlibet means to say:

          I have not heard the opening aria for such a long time, because this mixed bag of   
          variations has distanced me from it. The aria will now fly over the intervening mixed bag of 
          variations, to be repeated.

This idea is cultured, respectable, politically correct -- but contrived, and therefore dubious. I cannot help thinking that Bach meant something more earthy, as befits a quodlibet. My idea is based on the fact that the digestion of cabbage and turnips (like beans, lentils, cauliflower, broccoli, and Brussels sprouts) unfortunately produces flatulence -- so the quodlibet means to say:

          I have not been with you for such a long time, because the unfortunate result of your 
          fondness for cabbage and turnips has driven me away.

Brillat-Savarin wrote: "Tell me what you eat and I will tell you what you are."