This song is a play on the painting by Johannes Vermeer called Girl With A Pearl Earring. The painting is mysterious because there are more questions about the girl than there are answers.
For example, does she look happy or a little sad? Is she turning towards the viewer or away? What is the moment at which we are seeing her?
Some of these questions are answered in the Girl With A Pearl Earring song. And they are answered uniquely because the song is a male and female duet.
This song was originally intended to only have a male vocalist, but there wasn’t enough variety in the sound. So a female vocalist was added relatively late in the process of writing and recording this song. In hindsight, that was always the right idea, but it didn’t feel immediately obvious.
Here is a page with other songs about art.