Explain the function of music in Twelfth Night.

Though we seldom seem to think about it, history tells us
that many of the productions of Shakespeare's plays included music. Most of the music
itself has been lost, but, in fact, song lyrics are a big part of the play
Twelfth Night. Most of the music also centers around the character
of Feste the Fool. He is an entertainer and he "lives by the tabor," in other words, he
makes some of his money singing and playing for the various households. He is mentioned
in passing as a performer, and he is seen playing an instrument and singing in several
scenes. So, in addition to the function of entertaining the audience, and setting the
tone of the action in the various scenes where it occurs, music has another function in
the play in that it further defines Feste's character and reinforces that he is, indeed,
an "allowed fool" rather than just foolish.