The first song that Feste sings in Act 2, Scene 3 is a love song. Essentially, the song is about waiting for love. The first line speaks of a woman who is roaming about in search of her true love, while the second line tells the woman to wait because her "true love" is coming. The song further states, "Journeys end in lovers meeting," meaning that the search for love obviously ends when lovers finally meet each other. The first five lines in the song speaking of lovers meeting are particularly applicable to the theme of love found in the play. Both Olivia and Orsino are in search of love. Orsino thinks his journey for love will end when he finally wins Olivia, while Olivia feels hers will end when she finally wins Cesario.
The final line in the song, "Every wise man's son doth know," is also particularly applicable to the theme of love, but more specifically to the theme of the foolishness of love. In fact, one of Feste's roles in the play is to illustrate the theme of the foolishness of mankind by showing how all the characters are foolish but himself. What is important about the final line is that it's saying it is the wise man's son who knows about love, not the wise man himself. Therefore, the final line is implying that lovers are very foolish. The theme of the foolishness of love is even illustrated by the behavior of both Orsino and Olivia. Orsino's foolishness is illustrated in his relentless obsession over Olivia, while Olivia's foolishness is illustrated in first her groundless rejection of Orsino and then the fact she falls in love with a man who is obviously not a real man due to his obvious feminine characteristics. Hence, Feste's first song is significant in that it embodies two of the plays themes, the quest for love as well as the foolishness of love.
The second song found in Act 2, Scene 3 is part of an English ballad that was popular in Shakespeare's day. It's sung between lines 94 through 104, and both Sir Toby and Feste take turns singing lines from the song. The song appears to be about death, but Sir Toby and Feste are wittily using it for other meaning. The first line, "Farewell, dear heart, since I must needs be gone," is used as a reference to Sir Toby's rowdiness (94). He is using it to refer to the fact that he is making a disturbance in the house and either needs to quiet down or leave the house. Then, Feste and Sir Toby both use other lines of the song to wittily tell Malvolio to leave them alone, such as, "Shall I bid him go?" (101). In general, the song is important in that it captures the festive, comic spirit of the play.