Entertainment happeningsBlack Orpheus flick, tomorrow 2 and 7.30 p.m.. Union Theatre. Part of the SA film series, this flick, directed by Marcel Camus, deals with the Orpheus-Eurydice myth replayed in modern Brazil, as a streetcar conductor falls in love with a girl fleeing a man sworn to kill her. • • •The April SA film series is the Apu Trilogy directed by India's Satyajit Ray. On April 14 the Wednesday series begins with Pather Panchali, followed by Aparajito on April 21. The following Wednesday, 'The World of Apu will be shown. All films shown at 7:30 p.m., in the Union Theatre.• * *Desert Music Festival, June 11-13, featuring the Who, Lee Micheals, Neil Young, Buffie Saint Marie, Traffic, Sweetwater, Poco, Quicksilver, Credence Clearwater Revival, Canned Heat, Doors, Richie Havens, Mothers of Invention. For further info., call Anthony Ball at 584-2610. Tents, OK.• • *oils, and inks and recently gave up a career as a commercial artist to devote himself to painting.* * *Upstairs Theatre Downtown celebrates the world premier of Command Performance, written by Jon Manchip White, visiting professor of English at U.T. El Paso. Command Performance opens on April 8, 8:30 p.m., at the Upstairs Theatre Downtown, 717 East San Antonio. It will be performed each Friday and Saturday through June 1. ,# • *Sonny James, top country singer, appears Friday, 8 p.m., with the Southern Gentlemen at the ENMU P.E. Complex, Portales, N.M.• • *Rock group, Frigid Pink's next single release will be an updated version of Elvis Presley's Heartbreak Hotel. Frigid Pink are noted for an updated version of the Animals' House of the Rising Sun.