Mstislav Rostropovich has finished his first stint as music director of the National Symphony. He will return Jan. 10, in a French program, to begin the second half of his first year's concerts. Today seems an ideal time to examine some changes he has already made in the life of the orchestra and its patrons.

First, Rostropovich placed a sign in the Kennedy Center lobby on NSO concert nights that reads "National Symphony concerts begin promptly at 8:30 p.m." The orchestra's starting times had gradually deteriorated to the point that they often began much nearer 8:40 than 8:30. The same sloppy and completely unnecessary dilatory process has become something of a standard at both Washington opera performances and concerts sponsored by the Washington Performing Arts Society.

Now that the National Symphony has returned to starting times that are clearly printed on every ticket (as the Philadelphia Orchestra has always done), surely the opera company and the WPAS should follow suit. Everyone who goes to the Kennedy Center knows about the parking situation. If music is truly the central factor at every concert and opera, it is intolerable to permit people to stroll down the aisles once the music has begun. The Kennedy Center should remind its ushers of this regulation.

Second, Rostropovich ruled that the orchestra would tune up backstage rather than onstage just before the concert begins. This same change had been ordered once before - more than a decade ago. But at that time, and because the manner of its ordering stimulated a wide public debate, the change was strongly opposed by both the public and players alike. The rule was revoked shortly after its institution.

This season it seems not to have aroused any large public opposition, though you can hear people each week who say they miss the sounds of tuning up. And there are members of the orchestra who feel more secure if they tune up after taking their seats on the stage. Here is a bonus for those who make the effort to get to NSO concerts early and who also like to hear the orchestra tuning. The musicians can sit onstage and tune up all they want to, up to 8:15. At the time, they all leave and the stage doors are closed. So if you miss the old way, and want a little headroom before that 8:30 starting time, get there before 8:15.

(Incidentally, someone at last Sunday's performance of "The Magic Flute" was overhead saying that the practice of tuning up backstage was a Russian tradition. It is not Russian but European and fairly widely followed on that continent.)

Along with these changes, Rostroporich made a change in the seating of the orchestra, placing the violas on his extreme right, with the cellos who used to sit there now more nearly in front of him and angling back through the orchestra. Rostropovich also restored the use of orchestral risers as a standard practice in all concerts.

A less tangible but constant element that is also becoming almost a Rostropovich routine is the kind of ovation that often greets his entrances. There is no question that the National Symphony's new conductor generates an excitement in his concerts that has not generally been present on past NSO evenings. This is not an analytical evaluation of the way Rostropovich makes music. I feel it is still early for that kind of discussion. But there is a tremendous, almost measurable sense of anticipation and enthusiasm to be seen and heard from week to week. It bursts out when Rostropovich comes onto the stage.

It has to do with his obvious devotion to music and his eagerness to offer that devotion and that music to his audiences. It is also related to the open, unmistakable humility in his approach to music. There is something about the way he walks in carrying the score that emphasizes the manner in which he is soon to focus all his attention on the composer and the composer's intentions.

Last Monday when Aaron Copland was enjoying the wild ovations that surrounded his birthday party, a party given him by the National Symphony and its conductor, Copland said to Rostropovich, "What has happened to this town? It audiences used to be so staid!" The answer to that question at this point has to be: Rostropovich.