In that one moment, listening to that song, I became desperately aware of my need to touch this world somehow, and leave a legacy behind. I certainly am not the first person to feel this way. Perhaps all of us, somehow, are seeking meaning. Many of us long for immortality. Leaving a legacy is one way for us to become immortalized.
People create legacies in different ways.
Some people need to build something physical, like a skyscraper or a cathedral, to leave their legacy. Authors leave their books and articles. Songwriters leave their lyrics. However, it is unnecessary to leave behind something concrete in order to leave a legacy. What gives our lives meaning, I believe, is how we touch the lives of others.