THE MOST SPECTACULAR event in the history of opera took place on October 22, 1983 at the Metropolitan Opera's headquarters in Lincoln Center. It was the gala celebration of the Met's 100th birthday, televised live on PBS and filling more than eight hours of that network's time.

From the opening downbeat of James Levine conducting the "Bartered Bride" Overture in the afternoon to the final passionate notes of the Act II duet from "Un Ballo in Maschera" sung by Leontyne Price and Luciano Pavarotti in the small hours of the morning, it was operatic caviar. It demonstrated what the Met can do at its best.

Besides those already mentioned, the participants included Kiri Te Kanawa, Joan Sutherland, Frederica Von Stade, Birgit Nilsson, Judith Blegen, Montserrat Caball,e, Ileana Cotrubas, Grace Bumbry, Marilyn Horne, Placido Domingo, Alfredo Kraus, Nicolai Ghiaurov, Leonard Bernstein and a host of others. It was the most impressive collection of operatic talent ever assembled under a single roof at one time; some performances were better than others, but the high points were stratospheric, and the occasion itself was unique.

Those eight hours have now been distilled to about four, leaving out some of the less impressive moments and the delays between numbers, and the material can be seen and heard (in digital sound enormously better than television sound) on two LaserDiscs from Pioneer Artists (PA-84- 095, two discs with booklet). For those who like their opera sung by the stars and in highlight excerpts, it is sure to be the most significant recording of the year and perhaps of the decade.

So far, this material is available only in the LaserDisc format, which can be played only on specialized laser video disc players (not the CED system sponsored by RCA). No plans have been announced to lease it in any other format, though there is plenty of other Metropolitan Opera material available on LP.

At the moment, the most spectacular Met LP collection is the RCA set "Met: 100 Years, 100 Singers" (CRM8-5177, 8 LPs with booklet). A smaller package, the first of several in a series called "One Hundred Years of Great Artists at the Met," features "The Johnson Years," 1935 to 1950, when the Met was directed by Edward Johnson. Voices from those years featured on the set (MET 404, two records with booklet) include Zinka Milanov, Jussi Bjoerling, Kirsten Flagstad, Lauritz Melchior, Ezio Pinza and many others who have become legendary.

More information on this set, and also on special recordings of vintage Met radio broadcasts, can be obtained from the Metropolitan Opera Guild, 1865 Broadway, New York, NY 10023. The Pioneer LaserDiscs (and a list of other fine operatic productions in this high-tech medium) can be found in some local shops or ordered from Pioneer Artists, 200 West Grand Ave., Montvale, NJ 07645; or Starship Audio-Industries, 605 Utterback Store Road, Great Falls, VA 22066.

THE METROPOLITAN OPERA -- At the Kennedy Center Opera House through Saturday: "Simon Boccanegra" 8 Friday; "La Boheme" 2 Saturday; "Eugene Onegin" 8 Saturday.