"Show of Titles" will be a rousing and memorable celebration of title songs from more than two dozen Broadway musicals spanning nine decades, ranging from "Lady Be Good" to "The Light in the Piazza." But is the original title song disappearing from the theatrical map? What used to be the norm has become a rarity. Tony nominees, for example, from the 60's frequently had title songs. Contrast the 1965-1966-67-68 seasons when 75% of the nominated musicals had title songs, with the three most recent seasons when there was no original title song from a Tony-nominated Broadway musical.