In January, in our story about promising Pinellas artists under the age of 25, the Planet told readers to watch out for composer Dylan Glatthorn. Well, here's your chance to see what this music-theater wunderkind can do: The ever-lively Studio@620 is presenting a workshop performance of Glatthorn's new musical, Manifesto, this Friday and Saturday. It's a sweeping Irish historical romance and the composer (now a student at NYU) told us that he hopes its next stop will be Off-Broadway. [Note: See next week's Planet Picks for news of work by another promising young artist profiled in that January issue.] Fri.-Sat., July 21-22, 7:30 p.m., 620 First Ave. S., St. Petersburg, $10 general/$5 students and seniors, 727-895-6620.