The beauty of Da Vinci's Mona Lisa is how he did it. It's the record of his performance, so to speak. With a visual work of art, the "performance" and the thing performed are one and the same. It's more like a recording of a song than the song itself. I believe if other artists had painted from the same model, their "performances" would be equally valid.

I personally wouldn't want to paint the Mona Lisa - it's been done. If people have the same general feeling about a song, that song is a relic.