For the first half of its concert at the Kennedy Center on Saturday night the Boston Symphony Orchestra played at the durable, but safe, level that characterizes the prevailing standard of the international superorchestra.

In the second half it played like the Boston Symphony, in Tchaikovsky's exultant, exuberant Second Symphony, the "Little Russian." The performance positively burst with e'lan.

There were all the qualities that make the difference between the Boston Symphony and so many other ensembles. The orchestra sounded forth, but there was no bluster. Ensemble was superb. Brass, strings and winds blended almost like chamber music in passages demanding the trickiest articulation and some elusive balances. One was impressed not so much with the flawlessness as with the finesse.

This kind of playing happens only when the players are listening to each other as much as watching the conductor. The musicians of the Boston Symphony dash into this kind of musical opportunity with obvious relish (one example, the delectably colored, swaggering gait of the solo bassoon at the end of the first movement).

It was, of course, hard to tell just exactly how much control of the interpretation was being molded by the conductor and how much by the players. But music director Seiji Ozawa was giving his players maximum leverage.

The Tchaikovsky Second, based in part on Ukrainian folk themes, has an incomparable zest about it -- and an absence of the cumulative neuroticisms that would dominate the more famous Fourth, Fifth and Sixth. With its extensive solo segments (Charles Kavalovski's superb horn playing at the opening was properly rewarded in a bow requested by Ozawa), it probably suits itself better to this kind of free-spirited approach than do the other symphonies.

Free spirit did less for the two other works than for the Tchaikovsky. They were Haydn's Symphony No. 7 in C ("Le Midi") and a one-movement piece for guitar and orchestra called "To the Edge of Dream . . . . ." by the Japanese composer Toru Takemitsu. Manuel Barrueco, a winner of Baltimore's Peabody Competition, was the soloist.

The guitar composition, first performed in March 1983, was an evocative work basically on the same wavelength -- despite its ethnic roots -- with the Spanish works for guitar and orchestra. Appealing, but not saying anything especially new. The Haydn was polished, and bland.