The quadrennial spectacular starts with a splash Saturday at 6: The official opening ceremony at the Lincoln Memorial will feature not only the Mormon Tabernacle Choir, but also dancing colored fountains in the Reflecting Pool.

Not all of the inaugural events require invitations: There are dozens of free public activities that start this Friday.

On Friday at 7 there's a choice of the U.S. Marine Band Chamber Orchestra at the Museum of Natural History, Tenth and Constitution NW; the Romantic Chamber Ensemble at the Renwick Gallery, 17th and Pennsylvania NW, or the Seldom Scene bluegrass band at the National Air and Space Museum, Seventh and Independence SW.

Saturday, in the pendulum area of the Museum of American History, 14th and Constitution NW, it's barbershop quartets at noon, jazz by Hot Mustard at 1:30 and the U.S. Army Chorus at 4. Sunday there will be jazz at 12:30 and bluegrass at 3. In the Hall of Musical Instruments there will be chamber music at noon, 2 and 4, Saturday and Sunday.

At the Museum of Natural History Saturday, military bands and singers perform from noon till 6 and the Buck Hill Quintet plays jazz at 6:30. Sunday, it's gospel at noon, Mexican music at 1:30, Irish at 4 and bluegrass and chamber-music concerts at 7 -- in different halls. Monday U.S. Coast Guard Academy groups will sing at 11 and noon, and there'll be jazz at 12:30, blues at 2:30 and chamber music at 3.

The National Air and Space Museum presents Cajun and Appalachian music and dance at 2 and 6:30, Saturday and Sunday.

At the Hirshhorn Museum, Eighth and Independence SW, there will be Japanese music by the Toho Koto Society at noon Saturday and Sunday, country music by the Buddy Charlton Band at noon Monday and comtemporary chamber music by the 20th Century Consort at 3, all three days.

The Renwick Gallery has chamber music at noon, 2, 4 and 7, Saturday and Monday; at noon, 4 and 7 Sunday; and contemporary American songs Sunday at 3.

The National Museum of American Art, Eighth and G NW, presents chamber music at noon and jazz at 3, Saturday, Sunday and Monday.

At the National Portrait Gallery, Eighth and F NW, there's classical piano at noon and chamber music at 3 Saturday and Monday. Sunday it's jazz and popular music at 1 and chamber music at 3.

The Arts and Industries Building, 900 Jefferson Drive SW, has 2 o'clock string band concerts by Magpie (Saturday) and the Double Decker String Band (Sunday).

The Museum of African Art, 316 A Street NE, will present the Bill Harris Quartet Sunday at 2.

And in the Castle, 1000 Jefferson Drive SW, classical guitarist David Perry performs Saturday at 2 and Sunday at 1.

The U.S. Botanic Gardens will welcome the new president by surrounding a miniature of the White House with hundreds of yellow and white chrysanthemums. The free show will be open from 9 to 5, Sunday through next Saturday, at First and Maryland SW. Call 225-7099.

And remember, the kernel of all this rejoicing, the swearing-in, occurs on the West Front of the Capitol at 11:30 Tuesday, followed at 1:45 by the parade down Pennsylvania Avenue. For those who don't have parade tickets, the best viewing is between Fourth and 13th streets NW.

After the swearing-in, the West Front will be the scene of a free concert of patriotic music from 3 to 5, ending in a fireworks show said to be bigger than the Bicentennial's.