IT IS UNLIKELY, scholars tell us, that Mozart or his librettist, Lorenzo da Ponte, knew Haydn's opera, Orlando Paladino , which was dashed off hurriedly for a special occasion in 1782. And I suppose it is well to be assured of that; the concept of plagiarism does not apply to 18th-century opera as rigorously as it does to modern works of art, but one would hate to think that the characters of Don Giovanni, Leporello, Donna Anna and Don Ottavio, their interrelations and their motivations, had been stolen (even subconsciously and with great changes) from another opera.

And Orlando Paladino , as an ecstatic first hearing should convince you, obliquely foreshadows the Mozart masterpiece of five years later in some striking ways - not least in the sheer quality of the music, but also in the characters of the obsessed knight, his comic squire, the heroic soprano and the well-meaning but rather reckless tenor. The plot is entirely different, of course; and Haydn's music, for all its splendor, does not aspire either to the full emotional depth or the demonic overtones that can be found in Mozart's work. But Orlando Paladino is a masterpiece, and it is the only non-Mozartian opera of the 18th century that cries out for any kind of close comparison to Don Giovanni .

The Chronological accident that puts Orlando Paladino first is fortunate. If the dates had been reversed, Haydn (who has suffered more than his share of critical condescension in the past two centuries) would certainly have been branded an imitator. He is rather, of course, one of the most intelligently original minds in the history of music, and his opera helps to document the fact.

The world premiere recording of Orlando Paladino on Philips 6706 029 (four records) is the third Hayde opera premiere produced by that company with Antal Dorati as music director and a first-rate cast; it does the music complete justice, and that alone is enough to make it one of the outstanding records of 1977.

Just as a good Leporello can come close to stealing the show in Don Giovanni , baritone Domenico Trimarchi (as Pasquale, a squire mush like Leporello rises above his subsidiary role in this production.He is a coloratura baritone, a curious fact hilariously demonstrated in "Ecco spiano, " an aria about his singing ability, and he provides splendidly a major share of the comic element in this serio-comic opera. Another nuance - mock-heroic - is supplied by baritone Benjamin Luxon, who sings with a fine swagger as Rodomonte, King of Barbary and implacable foe of the love-maddened knight, Orlando (sung well but not outstandingly by tenor George Shirley). Mezzo-soprano Gwendolyn Killibrew, whose statuesque voice supplies a good audio equivalent of a commanding stage presence, adds yet another dimension. She is the sorceress Alcina, who turns Orlando to stone at one climactic point in the plot (another curious, though slightly skewed, pre-echo of Don Giovanni , where a statue comes to life), and in the end she takes Orlando down to the River Lethe for a drastic but effective cure for his lovesickness. Outstanding among the other singers are Elly Ameling as Eurilla, a shepherdess; Arleen Auger as Angelica, Queen of Cathy (and object of Orlando's hopeless passion) and Claes Ahnsjo as the Saracen warrior Medoro, Angelica's beloved.

The plot (as might be guessed from the paragraph above) is the kind of potpourri common in 18th-century libretti: a love-triangle, a bit of the supernatural to allow spectacular stage effects, a lot of comic byplay and some splendid heroic posturing - including a duel in which, delightfully, the swords clash in perfect time with the music, adding to the orchestra some charmingly unorthodox percussion. No matter, it all fits together well enough, with the aid of a sorceress exmachina at the end, and it gives a pretext for some exquisite music which Dorati, the singers and the Lausanne Chamber Orchestra perform gloriously.

This recording, with the two previous Dorati-Philips productions of Haydn's reputation closer to that of Mozart, which is where it belongs. The two composers, so different in temperament and style, though they were close friends and clearly influenced one another, stand apart from all other composers of the classical and romantic period by virtue of their incredible productivity and the universality of their musical talent. Schubert or Beethoven might have become notable operatic composers in other circumstances, and Wagner might have developed into a significant symphonist. But in fact, no other composer after Handel equals these two in abundance and variety, with such a high productivity and such uniform excellence in composing operas, symphonic works and chamber music.

At the opposite end of the spectrum from Haydn's operas, a recording of his piano sonatas adds less spectacularly to his reputation, partly because they have not been so shamefully neglected in out time (it's easier to record a solo pianist than a whole opera cast) and partly because their quality is less spectacular. Still, beyond the purely musical pleasure which abounds, there is a special kind of joy in the six records of Telefunken set SHD 25 123-T/1-6, which present Haydn's piano sonatas Nos. 1 to 34 in immaculate performances by pianist Rudolf Bushbinder.

The pleasure is that of watching a musical form grow and develop, beginning with the 19 early sonatas written primarily for teaching purposes (Hayndn gave keyboard lessons before he became a Kapellmeister ). These pieces are simple and rather square cut, but enjoyable to hear; and they show occasional flashes of genius. The increasingly flexibility and complexity of structure, even among these early works, reflect the growth of an artist who was to continue growing through nearly half a century.

After he became the music director at Esterhaza and stopped having to write with the limitations of students in mind. Haydn's piano sonatas took a quantum leap, shown to some extent in Sonata 20 but most clearly in the sonatas beginning with No. 29 of this collection, which seem to have been composed with an audience in mind and have considerably more sophistication. The final sonatas of this set date from the beginning of the composer's mature period and begin to have features in common with hiis orchestral works. Sometimes they balance the left hand against the right in a style like that of a concerto - strikingly similar, in fact, to Bach's Italian Concerto .

Even in his later sonatas, which are not in this first volume, Haydn never achieved or even attempted the kind of stromy emotionalism found in Beethoven's greatest piano works; that was not part of his keyboard style (though he did explore strong feelings in some of his middle symphonies), and the pianos of his time would not have been able to handle such treatment. But from the very beginning, even the trifles are trifles produced by a giant, and it is a pleasure to watch him stretching toward his full growth.

It may be well to mention that there are not 34 complete sonatas by Haydn on these six records, although it does contain sonatas 1 to 34. Two of the works included, Nos. 17 and 18, were discovered only in recent years and are attributed to Haydn with some hesitation. Eight others are known only in fragments (chiefly the identifying the matic material Haydn wrote down in his personal catalogue of his works), and those fragments are played by Buchbinder on a seven-inch record packed in with the half-dozen 12-inch. records of this set. Anyone knowing the whereabouts of Sonatas 21-28 hereby requested to send copies [WORD ILLEGIBLE] dolf Buchbinder. I would like [WORDS ILLEGIBLE] him play them.