The audience for the National Symphony's inaugural concert in the Concert Hall last night went through the tightest security checks in Kennedy Center history. Tickets were shown immediately upon entering the Grand Foyer, and again when proceeding through special ticket-taking booths placed in the lobbies where armed police patrolled.

It was the last of three concerts attended by the president-elect and Mrs. Reagan at the Center on an evening of traffic jams outside and nonstop celebration inside as people came and went throughout the building.

Ten minutes before the concert was to begin, the Reagans and Vice President-elect and Mrs. Bush went backstage to meet the artists they were soon to hear: Mstislav Rostropovich, music director of the National Symphony, and pianist Eugene Istomin.

The program was a skillful mixture of music of extreme popularity and music of the highest genius. After a "Star-Spangled Banner" that profited powerfully from the singing of the large men's chorus on stage, Rostropovich conducted Erich Korngold's razzle-dazzle title music from "King's Row," described in the program as "the film for which Mr. Reagan earned the greatest admiration as an actor." This was followed by a tremendous performance of Randall Thompson's "Testament of Freedom," last heard at a presidential inaugural concert in 1961 when it was performed in Constitution Hall for incoming president John F. Kennedy. Its words by Thomas Jefferson speak as tellingly for our times as they did when they were written between 160 and 205 years ago. The men of the Choral Arts and Oratorio societies sang the music compellingly and with flawless enunciation.

Just before the intermission, Rostropovich launched the orchestra into a vivid delivery of Sousa's "Stars and Stripes Forever," during which many in the audience clapped in rhythm. During the Sousa, the Reagans and Bushes departed, which acted as a signal for others to do the same. Many in the audience, obviously unaccustomed to concertgoing, talked during much of the music, even to the extent of performing introductions in boxes when cabinet designees entered late. There was also, as could be expected, generous applause between movements of Thompson, and just as freely, at the pauses in Mozart.

It was in the Mozart Piano Concerto in C Major, K.467, that the evening's great music arrived. Istomin played with magnificent style, by turns appropriately lyrical and witty. He also contributed a cadenza of ingenious beauty. The orchestra's handsome support was given with great spirit. It was a performance that should be heard again in more conducive circumstances.