The Magic Theatre, which recently just mounted two legacy revivals of plays that were produced at the Magic early on in their respective lives (Sam Shepard’s Fool for Love and Paula Vogel’s The Baltimore Waltz), has returned to their original mission of producing world premieres with Han Ong’s new play Grandeur, about the life of Gil Scott-Heron, the spoken word poet who is generally considered to be, along with Coke La Rock, the very first rap artist. While the play is a rarefied experience and formally almost diametrically opposed to rap music, there’s no doubt that Grandeur is the first draft of a major American drama, and while it doesn’t appear to be finished in its current production, it still shows enough sparks of genius to be absolutely worth a trek to the Marina District in San Francisco to see it.