I'd appeal to why the musician is "independent". If I am to guess because the musician wants control over his/her career and creation; away from big record labels dictating his/her career. The same approach can be said for moving to Nostr (control). You can appeal for value for value. I'd also appeal what are the problems of independent musician experience in centralised social media? I'd assume that his/her entire account could easily be banned with one mistake and if this is something the musician can afford to lose? Those are some examples but not comprehensive. The bottom line, appeal to their existing problems and how Nostr can solve or provide opportunity. 👍👌☺️