In his nine seasons with the National Symphony, first as music director and the last two years as principal guest conductor, Antal Dorati has given equal attention to two areas he felt the orchestra particularly needed to strengthen: technical discipline and repertoire.

Dorati, who now heads the Detroit Symphony, will conclude his ninth season with the National in a series of concerts in the coming three weeks.

One of Dorati's first moves after taking the National Symphony post in 1970 was to study its past programs, a study which soon led him to observe: "It will not be difficult to give first NSO performances of many master pieces." Among those he proceeded to introduce were symphonies by Hyadin, Bruckner and Mahler.

Dorati displayed another facet of his broad musical genius when he placed - in modest numbers - his own compositions on NSO programs. Among the happiest of these was his "Chamber Music" for soprano and orchestra in which Heather Harper sang the unusually fragrant, evocative settings: theDivertimento for oboe and orchestra and the concertos for piano and cello.

Although familiar symphonies by Haydn and Berlioz comprise this week's concert, next week Dorati will add a lustrous novelty to his list of local premieres when he leads the first National Symphony performances of Zoltan Kodaly's "Peacock Variations." With its symbol of great Hungarian national pride, this is one of Kodaly's finest orcestral works, and one that belongs in the repertoire of any major orchestra today.

The following week, another Dorati composition will precede the Mozart Requiem: His own new song cycle, "Voices," a setting of nine songs to poems for Rainer Maria Rilke. It was written for the Swiss bass Peter Lagger, who has been heard in Washington under Dorati's baton.

The original version of the songs was written at Christmas 1976 at the singer's request. "Already when composing that piano version," Dorati says, "I knew that the piece would find its ultimate expression with an orchestral treatment." That second and final version had its world premiere last October when Dorati and Lagger presented it with the Stockholm Philharmonic. The coming NSO performances will mark not only the U.S. premiere of the songs but also their first presentation in English.

"The English translation" - it is imperative that these songs be interpreted in the language of their audience - "is my own," says Dorati. He adds that he took special care not only to "transform the German text into idiomatic English but also to provide the necessary prosody . . . and thus present a new, original work, as which the piece here offered should be regarded."

There are arresting parallels between Dorati, Rilke and the history of the National Symphony. Dorati's permanent home is, as it has been for some years, in the tiny Swiss village of Walchwil on the Zugersee. It is no great distance from there to the hamlet of Val-Mont, near Glion (now called Ilanz) where, on Dec. 29, 1926, Rilke died. And it should be recalled, especially with the National Symphony's 50th anniversary year coming up shortly, that its founding spirit, the indomitable Mary Howe, who was also a composer of note, included among her finest songs, settings of Rilke's "Schlaflied" and Liebeslied."

For "Voices," Dorati has not turned to the deeply touching mood of "Schlaflied," which begins, "Some day, when I lose you," and ends with an ineffable phrase, "Leaving you closed, with a mass of star flowers and melissa . . ."

Nor has he chosen from among the famous Duino Elegies, or the mysteriously full-flowered Sonnets to Orpheus, all of which were written in that era about which Rilke later was to say: "February 1922 was my big time!"

Rather, for "Voices," Dorati went to some of the bitterest poetry of the first quarter of this century. The individual poems in his new cycle, following a Prologue and a closing Farewell, are songs of the beggar, the blindman, the drunkard, the suicide, the widow, the idiot, the orphan, the dwarf and the leper. At the end of the songs, Dorati repeats the lines heard at the beginning, "The rich men, the fortunate and happy can well be silent . . . but the unhappy ones may cry out - weeping."

Then, and perhaps most significantly of all, Dorati the composer goes a step beyong Rilke the poet. Unwilling to leave his "voices" in unending misery, Dorati says, "It is unthinkable not to offer at least the thought of possible consolation after Rilke's stark, provoking revelation of human sorrow." For this purpose, Dorati has added lines inspired by the Beatiudes: "They shall be heard . . . and shall be comforted."

But Dorati's contributions to Washington's music lovers this spring will not end with his NSO finale on April 13. On Sunday, April 29, Dorati will return with his Detroit Symphony to present a complete performance in concert form of "The Egyptian Helen" by Richard Strauss, with Gwyneth Jones in the title role.

One of the least-known of Strauss operas, with its text by Hoffmansthal, the "Egyptian Helen" is rarely heard, though some of its music is of great beauty. Immediately after the Washington performance, which follows one in Detroit, the whole thing will be recorded under Dorati's direction on London Records, where it will probably garner another of the prizes for outstanding recordings with which Dorati helped to put the National Symphony on the world's major musical maps.

There are many solid reasons for the special warmth that greets Dorati each time he returns to conduct here. CAPTION: Picture, no caption