Tot Rock: Rocknoceros jammin’ at the Smithsonian, for ages 2-6, with Coach, Williebob and Boogie Woogie Bernie, a complimentary cup of Jammin’ Java coffee and snacks served to the grown-ups. 10:15 and 11:30 a.m., Discovery Theater at S. Dillon Ripley Center, 1100 Jefferson Dr. SW. $8; ages 2-16, $6; 1 and younger, $3. 202-633-8700 or www.discoverytheater.org.

Behind-the-scenes cathedral tours, for age 11 and older, close-ups views of gargoyles and stained glass windows; views of the city from on high, cameras recommended. 10:30 a.m. most weekdays and Saturdays, Washington National Cathedral, Wisconsin and Massachusetts avenues NW. $10. 202-537-6200 or www.nationalcathedral.org.

African Americans Dedicated to Gettysburg, procurement technician Yolanda Bean discusses the Gettysburg campaign. 10:45 a.m., National Archives, Room G-24, Constitution Avenue and Ninth Street NW. Free. 202-357-5000.

“It’s Show Time: Sheet Music From Stage and Screen,” a lecture by the music division’s Sharon McKinley. Noon, Library of Congress, Jefferson Building, Whittall Pavilion, 10 First St. SE. Free. 202-707-5502.

“Rothko’s Rooms,” a documentary about the creation of the room designed for Rothko’s Seagram Murals in London’s Tate Modern. 12:30 p.m., National Gallery of Art, East Building, Constitution Avenue and Fourth Street NW. Free. 202-737-4215.

American music abroad, the Dennis Luxion/Michael Raynor Quartet performs original hard-swinging jazz inspired by saxophone improvisation. 6 p.m.; Legacy performs an alternative hip-hop sound influenced by West African, house, jazz and breakbeat genres of music. 7:15 p.m, National Geographic, 17th and M streets NW. Free. 202-857-7700.

Classical music concert, students from the Juilliard School perform. 6 p.m., Kennedy Center, Terrace Theater, 2700 F St. NW. Free. 202-467-4600.

The Glamorous Age of Empress Elizabeth Petrovna, Ekaterina Khmelnitskaya discusses the daughter of Peter the Great, Empress Elizabeth, and her reign over a period of Russia’s artistic history including her founding of the Imperial Porcelain Works in 1744 and pieces of table decoration that enhanced the balls, dinners, masquerades, concerts, and firework displays. 6:30 p.m., Hillwood Estate, Museum and Gardens, 4155 Linnean Ave. NW. $10; college students, $7. 202-686-5807.

“The Enigmatic Frank Sinatra,” American popular music specialist Robert Wyatt discusses the crooner’s life of meteoric shifts from immense popularity to being out of favor, plays some of the songs he immortalized and shows clips from films he made over a 40-year period. 6:45 p.m., National Museum of the American Indian, Rasmuson Theater, Fourth Street and Independence Avenue SW. $40. 202-633-3030.

“The Mystery Plays,” drama students perform Robert Aquirre-Sacasa’s two interrelated one-act plays based on medieval mystery plays but infused with the eerie sensibilities of the modern American horror genre. 7:30 p.m. Thursday, 2 p.m. Saturday-Sunday, Catholic University, Hartke Theatre, 3801 Harewood Rd. NE. $15; seniors, $8; students, $5. 202-319-4000.