From The Sound Guy:
PlayLyrixÃ?Â¢Ã¢??Ã?Â¢ searches your iTunes collection and automatically creates a new playlist of all the songs whose lyrics contain specified words or phrases.
PlayLyrix can be used to create playlists of songs with lyrics that reinforce a variety of moods or themes. For example, if today is your birthday, you might want to make a playlist of all your songs that have the word "birthday" in the lyrics. PlayLyrix will also create a list of songs containing the specified lyrics, including songs which are not in your iTunes library. Click on "Show lyrics" to see the song's lyrics, or click "Buy song" to purchase the song from the iTunes Store.