Brazilian cellist Antonio Meneses, who won last year's Tchaikovsky competition in Moscow, made a dazzling American debut last night at the Kennedy Center with Claudio Abbado and the London Symphony Orchestra, opening a world tour for the group.

Meneses' playing was simply magnificent, as was the playing of the orchestra and the conducting of Abbado.

Meneses performed the glorious and neglected Elgar Cello Concerto, which is just about as complete a test of a cellist's mettle as can be found in one composition. Meneses, who is 26, showed a commanding mastery of his instrument, which is a 1698 Guarneri, and of Elgar's touching, valedictory work.

From that startling recitative introduction for cello alone on, Meneses' tone was perfectly focused. Pitch was almost uncannily on the mark. And the sound of Meneses' playing is so large that not once was he covered by the orchestra, even at full volume. His low notes, which are normally the fuzziest part of the cello's sound, had a resonant solidity that recalled the sound of a great bass voice. That low note to which the cellist leaps at the end of the opening recitative was startling in its impact. Musically, the cellist played with great breadth and sensitivity, both to passing nuance and the overall grand line of the concerto.

Abbado, one of the world's greatest conductors, conducted the Elgar with exquisite attention to the concerto's myriad range of color, and the ways in which the instruments of the orchestra combine with the tone of the cello.

Under Abbado, the London Symphony's emphasis is on cohesion and balance. It is not quite the gold-plated Cadillac sound of the Chicago Symphony, of which Abbado is principal guest conductor and is presumed to be Solti's heir apparant. The London Symphony's sound is a little less resonant, but within that sonic frame it achieves remarkable clarity and precision.

As a result, over and over in the Webern Six Pieces, Op. 6, and in the Mahler First Symphony one heard details one had never heard before. Abbado conducted with his customary passion, his remarable sense of the pulse of a work and his grasp of the overall direction it is taking. There was great delicacy of nuance in the Webern, and the Mahler has never sounded mightier.