I once watched an episode of Ally McBeal that featured Ally (Calista Flockhart) and her therapist (Tracey Ullman). While lying on the typical leather couch, Ally is asked by her therapist to name her "theme song" - the one song that she feels sums up her life. At first, Ally thinks that maybe her therapist is the crazy one. As the show progresses, however, she realizes that most people have a song that they hear as their life is playing out. I think that this best explains why Allan Jay Lerner and Frederick Loewe added song lyrics to George Bernard Shaw's 1913 play, Pygmalion, when they turned it into their 1956 musical play, My Fair Lady, which George Cukor transformed to celluloid in 1964.
Some may argue that My Fair Lady is unrealistic because of all the singing added to it. I, however, believe that the songs do not take away any of the reality or integrity of Pygmalion. If anything, they make it better. By adding songs, Lerner and Loewe were better able to capture and hold the attention of the audience. People watching the musical play would be more apt to remember what the characters say because they can recall the song. The songs also serve as a great way to convey what the characters are thinking without them just speaking aloud to themselves. When one hears a character on the stage just speaking to himself, one begins to feel that perhaps the character is not quite right. In a musical play, however, the audience members are already expecting the songs, and therefore they are more open to receiving characters' thoughts without the use of conversation with another person. Speaking aloud to one's self is just thought of as part of the whimsical charm involved in a musical production.
But the most important reason that the songs are needed is that most people have a song that they hear during certain parts of their life. Adding songs to Pygmalion only voices the thoughts that people are having at a certain time, such as the song "I Could Have Danced All Night, sung by Eliza Doolittle (played by Audrey Hepburn and sung by Marni Nixon in the film) after she finally repeats the line "The rain in Spain stays mainly in the plain"; and she, Professor Henry Higgins (portrayed by Rex Harrison on the stage and screen), and Colonel Pickering (Wilfred Hyde-White) dance to show their jubilation at her feat. Another instance where a character's thoughts are best evident through song is Professor Higgins' last number, "I've Grown Accustomed to Her Face." Without the song, we would be unable to know precisely what Higgins was thinking at this stage.
To sum up, I believe that people who think that the songs in My Fair Lady are silly and unrealistic are wrong. Just like Ally McBeal, Eliza Doolittle, Henry Higgins, and Colonel Pickering express themselves every day through music.