ANTAL DORATI, whose 75th birthday was too little noted last April, is regarded (in this community especially) as an outstanding orchestra builder. In terms of repertory, he is an acknowledged authority on Haydn and similarly respected for his sponsorship of new and/or neglected music. He has also shown a remarkable promoter's flair for exploiting the blockbusters of the standard repertory in order to create receptivity for his "discoveries." o

In Dorati's all-too-few recordings as conductor of the Detroit Symphony Orchestra, an "1812" may have paid the freight for the stunning account of the Bartok First Suite, and a package of well-known rhapsodies (Liszt, Enesco, Dvorak, Ravel) may have offset part of the cost of the premiere recording of Strauss' opera "Die schweigsame Frau." Although Dorati has stepped down from his post in Detroit, the recordings are still coming; the latest, and in some respects the most intriguing so far, is the new digital disc of Karo Szymanowski's second and third symphonies (London LDR-71026).

This happens to be the first record of any of Szymanowski's orchestral music to be made in this country, and in fact the first, except for two of the concertos, to be made outside Poland. The fact that neither the conductor nor the orchestra is Polish is by no means unimportant: Less than 20 years ago, the first recordings of Carl Nielsen's symphonies to be made outside Denmark and with non-Danish conductors served to bring that master's works at last into the international concert repertory. The time may be ripe now for Szymanowski. (His opera "King Roger" received its U.S. premiere in concert performances by the Saint Louis Symphony Orchestra under Leonard Slatkin last May.)

Another first, apparently, is the use of tenor soloist (Ryszyard Karczykowski) with the chorus (the Kenneth Jewell Chorale) and orchestra in the Symphony No. 3, "Song of the Night." This sumptuous setting of the poem by the Persian writer Jallal-ud-din Rumi was written for these forces, but in its two prior recordings, both from Warsaw, a soprano was substituted for the tenor, a practice I understand is followed in most performances in Poland.

While Szymanowski did eventually enter a period in which Polish folklore was his central interest, both of these symphonies preceded that point. The Third Symphony belongs to his "Eastern" phase, and is probably the most pointed and concise of the several works he composed under the productive influence of Persian and other Islamic cultures -- and, in this 1915-16 score, that of Debussy as well.

The Second, composed five years earlier, reflects Szymanowski's allegiance, in his 20s, to Wagner, Strauss and the German tradition in general. Its outline, curiously, parallels that of Prokofiev's final piano sonata (Op. 111) -- in other words an opening fast movement of dramatic substance and only one other, quite a bit longer and cast in the form of a theme and variations. Szymanowski concludes his variations with a fugue, a la Reger.

Dorati's conviction is felt in every phrase, and both symphonies hold together here with a greater sense of flow than in any of their respective earlier recordings. The orchestral playing is on a very high level, the soloist and chorus in No. 3 are first rate, and the sound itself is all one could ask. A very happy occasion for admirers of this composer, and an attractive way for others to discover him.

Admirers of Vincent d'Indy have cause to celebrate, too. There has been no recording of his gorgeous Second Symphony since the old Monteux version was retired years ago, and even "Istar" has not held a permanent place in our catalogues. But now Arabesque has had the imaginativeness to obtain from Pathe-Marconi (French EMI) two discs of D'Indy's orchestral music, performed by the Orchestre Philharmonique des Pays de la Loire under Pierre Dervaux (8097-2; cassettes 9097-2).

"Istar" is the first item presented here, but the music is preceded by an old recording of the composer's voice, speaking for less than a minute of his "Wallenstein" trilogy. This music fills out the first disc. The second is given over to "Summer Day in the Mountains," "The Enchanted Forest" and "Tableaux de Voyage." The quality of some of these pieces is variable; not all the material reaches the level of "Istar," but it is all very much worth hearing. The sound is quite good, too, though less impressive than the French pressings.