When writing a song, what does a composer start with – the tune, or the lyrics? Do you come up with words to fit a particular melody, or do you read the words and imagine a tune that would fit the words? The answer is, different composers and lyricists work in different ways. For Gilbert and Sullivan, the journey from musical idea to finished song took an interesting path: Gilbert would write lyrics that fit a popular tune he had in mind. Then he would give the words to Sullivan, without telling him what song he’d used. Sullivan would study the rhythm of the words and come up with a tune that…