What a great way to start the New Year! A slimmer Mstislav Rostropovich walked out in front of the National Symphony Orchestra last night at the Kennedy Center and opened up with some of the most gala of all music, the overture to "Ga ite' Parisienne."

The only trouble was that there was far too little of Offenbach's champagne sounds. Before you could remember the starry names of Leonid Massine, Frederic Franklin and the matchless Alexandra Danilova --who danced in the 1938 premiere-- it was over. Please, Mr. Rostropovich, play much more the next time. At least the cancan.

There was, however, still plenty of glitter left in the evening. Jean-Pierre Rampal, who will celebrate his 60th birthday tomorrow, is playing his edition of the Khachaturian Violin Concerto with the NSO four times this week. For 35 minutes it must make him the fastest flute in the world. Looking nowhere near his certified age, Rampal tossed off prestissimo scales and arpeggios, adding his own brilliance to the cadenzas. And in the lyric moments when things slow down for a bit, his tone had all its familiar, golden gleam.

The transfer from violin to flute works well enough. Both instruments need protection from the full orchestra, both excel in rapid figurations and sustained melodic lines. The music itself is largely a matter of color, mood and effect, longer than it needs to be, but showy in the exotic, 19th-century Russian manner. Rostropovich had the orchestra playing with every ounce of plush desired.

The evening's nobility came in Rampal's encore, a Bach Sarabande, and the Second Symphony of Schumann. This Rostropovich opened solidly, achieving a beautifully devised accelerando at the close of the first movement. The scherzo had echoes of Mendelssohn with delicate treatment of the crucial changes in tempo. The slow movement was as moving as one of the great slow passages in music deserves; and the finale, with the trumpets especially impressive, was a powerhouse.

At the intermission, NSO board president Leonard Silverstein read a tribute to Lee D. Butler, who died on Dec. 31, only weeks after the orchestra honored him and Mrs. Butler for their 50 years of membership in and work for the National Symphony. He was one of those who made it all possible.