WHAT'S HAPPENING.

Treemonisha, an opera by the self-published African American composer Scott Joplin (1868-1917),will be performed in St. Louis at the Loretta/Hilton Center. Treemonisha was only performed once during Joplin's lifetime. The composer became so obsessed with the production's lack of success that he suffered a nervous breakdown and was institutionalized in 1916. The opera opens on Saturday, May 20 through June 25 and ticket prices are $18 to $80. For information, call 314-961-0644.... Art and Oracle: Spirit Voices of Africa at New York's Metropolitan Museum of Art (1000 Fifth Ave.; 212-535-7710) from April 26 to July 30 explores the connection between African art and religion.... Jazz saxophonist Joshua Redman has been appointed artistic director of the San Francisco Jazz Organization's "Spring Season 2000," which runs to June. For a concert schedule, call (415-398-5655; www.sfjazz.org).... Park your car at Denver International Airport and have it washed, polished and the seats Scotch Guarded while you're out of town. The Conoco Service Station (303-342-0303) offers the "Ultimate Detail" at $229.95: .... Jazz lovers raid New Orleans for the 31st annual Jazz & Heritage Festival (800-488-5252; www.nojazzfest.com), April 28-May 7. Tickets range from $15-$35 daily. Arrive early; shows get crowded.