For whatever it may mean in the cosmic realm, an Argentine pianist, Bruno Leonardo Gelber, and a British conductor, Raymond Leppard, achieved a close meeting of minds last night in the Schumann Piano Concerto, which they performed with the National Symphony at the Kennedy Center.

The point is not made just as an exercise in gimmickry. The lyric and fiery sides of this work are hard to bring into balance. But last night there was no sense either of rushing or of timidity--all with the steadiest of tempos. Gelber took a fresh, rhapsodic approach; the melodic line was strongly bent, but not the pulse.

Technically, everything seemed easy and--more to the point--graceful. In a tour de force like the first movement cadenza there was just power enough, without any blasting away.

The balances, usually a problem in this complex work, were splendid under Leppard. He reduced the orchestra to, among others, five basses. The result was clarity without any particular loss of force. The slow movement seemed slightly less ardent than the outer movements. It could have breathed a little more, and perhaps it will on the repeats tonight, tomorrow and Friday.

The rest of the program was all Sibelius, for whom successive generations of British conductors seem to have a penchant. There's something about Sibelius' stark monumentality that rouses the cozy English spirit.

First, there was an almost totally unknown work, a tone poem called "Night-Ride and Sunrise." It is a variation of a typical Sibelius formula, the tone poem that seems to rise in lonely string motifs and rich wind and brass fanfares to a sonorous climax. Spectacular examples of this form, such as "Tapiola," will stir the feelings, but this was less riveting. The subject is a nighttime train ride that develops into a grand sunrise. The four-note figure that represents the sound of the wheels (one assumes) gets a little monotonous. It's not a bad piece--just a bit short of the composer's best.

So is the First Symphony, but there's certainly nothing bland about its rhetorical pyrotechnics. It's a little like early Mahler mixed with Tchaikovsky, but not as good as either. Still, some of the tunes, like the broad second theme of the last movement, are hard to resist, as are the resonant brass and string sonorities. It's like taking a bath in sound.

Leppard's performance could have used a little more rhythmic punch. The interpretation was broad and atmospheric and, on the whole, quite splendid.