THE MESSIAH" does not exist - not only because Handel called it simply "Messiah," without the article, but because there was never in his lifetime a single established score, as there is for, say, "Scheherazade" or "Die Schoene Mullerin." During the reign of Queen Victoria (and in some places even today) it was called "The Messiah"-a mistake that is symptomatic of a whole state of mind.

George Frederick Handel's meditation on the life and work of Jesus Christ is a massive, complex work, requiring nearly three hours in most performances, but he dashed it off in less than a month (Aug. 22 to Sept. 12, 1741 for the first draft). He continued to tinker with it for the rest of his life, rewriting a melody to suit a particular singers' weaknesses, shifting a piece from alto to bass, cutting down an aria to a recitative, dropping or adding instrumental parts according to the orchestral forces available. Handel never published sheet music, as he did for most of his other big hits. Plates were ready to go to press in 1749, but the score was not published until 1763, four years after his death. In his lifetime, he even varied the number of soloists from four to nine.

His rewriting was only the beginning, however. For nearly two centuries after Handel's death, Virtually everyone who came along felt free to alter the music to suit changing tastes. One of the first was Mozart, who added the trombones, horns and clarinets that Handel had not included, as well as rewriting some of the music. This textual fluidity is fairly common today is musical comedies (for example, there is no single text for "Show Boat"), but seems a bit odd in the first of our true musical classics-that is, the first to have a continuous history of performance from its composition until the present day. Nobody can say for sure that "Messia" is the most-performed piece of music we have-not if we count all the 6-year-olds who are wading through "Fur Elise" on the piano. But at this time of year, when there are "Messiahs" by the dozen in the Washington area and by the thousands on the national level, it sometimes seems that it is the only music in the world.

King George III must be given some credit for creating the institution of musical classics, along with his other heavy responsibilities. It was largely because he would listen to no music but Handel's that Handel festivals became an annual eventin England, and the reworking of his music became a favorite pastime of later musicians.

While the music was being adapted, it was also growing in sheer muscle. A typical performance in Handel's lifetime had a chorus of about two dozen singers and an orchestra slightly more numerous (18th-century instruments were not as loud, on the whole, as those used today). But as the musica became a sort of national monument, it grew to monumental proportions. In 1786, only 35 years after "Messiah" was composed, Horace Walpole attended a festival performance in Westminster Abbey that involved over 1,000 performers, some playing extra-large bass instruments Handel had never dreamed of. It was "magnificent," he sai in a letter, "but the chorus and kettledrums for four hours were so thunderfull, that they gave me a headache."

Before it became a venerated and beloved classic, "Messiah" had its problems. The first performance was in Dublin, where Jonathan Swift, author of "Gulliver's Travels," was the dean of St. Patrick's Cathedral. When Handel tried to borrow some of the Cathedral's musicians for the world premiere of "Messiah" and other concerts, Swift refused categorically and colorfully to have anything to do with it. In a written statement, he threatened to punish any of his musicians who "shall ever appear there, as songsters, fiddlers, pipers, trumpeters, drum majors, or in any sonal quality, according to the flagitious aggravations of their respective disobedience, rebellion, perfidy and ingratitude."

Three things can be said in extenuation: Swife was then trembling on the brink of the madness in which he would end his life; he later relented, after mutual friends intervened; and he was not alone in his abhorrence of this new monster- a religious work being performed in a theater by that most depraved branch of manking, actors and actresses.

The next year, when "Messiah" was brought to London (very cautiously-Handel did not even publicize the name but simply announced "a new sacred oratorio") the controversy was enormous, and he was accused of profaning and profiting on religious sentiment. As late as the reign of Queen Victoria, a dean of Westminster Abbey banned "Messiah" from those sacred precincts, although it had already been performed there in the reign of George III.

As for profiteering, Handel undoubtedly did well on "Messiah," but so did many others. A large proportion of the performances in his lifetime were for charity, with the musicians donating their work. As noted by the leading 18th-century historian of music, Charles Burney, "This great work . . .has fed the hungry, clothed the naked, fostered the orphan and enriched succeeding managers of Oratories more than any single musical production in this or any other country."

His opinion of the music was somewhat higher than that of Charles Jennens, who compiled the text from the Bible and the Book of Common Prayer. In a letter to a friend, Jennens said of "Messiah": "He has made a fine entertainment of it, tho' not near so good as he might & ought to have done. I have with great difficulty made him correct some of the grossest faults in the composition, but he retain'd his Overture obstinately, in which there are some passages far unworthy of Handel, but much more unworthy of the Messiah." This makes Jennens, presumably, the firstin the long line of those who have tried to improve the music.

But despite the revisionary efforts, a first-rate performance of "Messiah" can be a listening experience that recalls the (probably apocryphal) quote attributed to Handel on the composition of the work: "I did think I did see all Heaven before me and the great God himself."