How does Feste's song from Act 2 Scene 3 of Shakespeare's 'Twelfth Night' relate to the themes and characters of the play?

In Act 2 Scene 3 of Twelfth Night Feste enters the scene to have a drink and share some jokes with Sir Toby and Sir Andrew, who are both by this stage very drunk. Sir Toby requests a song from Feste, and this is seconded by Sir Andrew amidst a paragraph's worth of meaningless gibberish that he spews forth in his intoxicated state. Feste asks of the two, "Would you have a love song, or a song …showed first 75 words of 1156 total…

…showed last 75 words of 1156 total…mostly directed at Olivia, but as has been said it does carry guidelines for practically anyone in the real world. It seems as though it should have quite a jolly little tune, and if I were to arrange it I would most likely set the underlying rhythm parts for a lute and possibly put a melody for a fiddle as well, these two being classic Elizabethan instruments and both capable of producing light, cheerful tones.