The two most famous American divas now singing, Leontyne Price and Marilyn Horne, join in two hours of arias and duets tonight on PBS (Channel 26, 9 p.m.). This concert, taped at the Met last spring, was only the second time they had sung together.

Price is as fine a dramatic soprano as there is, and Horne is as fine a mezzo as there is. Once the voices are warmed up -- which takes a while for the 55-year-old Price -- glorious vocal sparks burst in all directions. It isn't just a matter of "Anything you can do, I can do better," though there is some of that in the juxtaposed arias. The greatest excitement comes in the five Price-Horne duets, in which the two voices contrast and mesh to perfection. There is the sensuous Price, perhaps the most opulent voice of our time, against the razor-sharp Horne, a voice equaled only by the younger Nilsson in laser-like focus.

To the television camera, they make a striking contrast in manner -- Price with her regal bearing and fiery intensity; Horne with her plain-Jane cheerfulness, acting more with her voice than with anything else.

Because the careers of Price and Horne, who is 48, have taken such divergent courses and because the singers have so rarely crossed performing paths, there is only one duet that is in the regular repertories of both singers: the Aida-Amneris scene from Act II of "Aida."

In the others, we get these never-befores:

* A tantalizing taste of the Norma that people begged Price to do and she always backed away from, in the complete scene that ends in the famous "Mira, O Norma."

* Debuts by Horne as Puccini's Suzuki in the "Flower Duet" from "Madama Butterfly" and as Mozart's Dorabella in the duet from "Cosi fan tutte" in which the sisters itemize the qualities of their lovers.

* Price's first experience with a duet from Handel's "Rodelinda," a work Horne will bring to the Met next year as the first Handel opera to enter that repertory.

This concert is the most dramatic of Lincoln Center's and the Met's televised extravaganzas of the supersingers, and it is also the most substantial. Each soprano has three arias apiece. In addition, James Levine conducts the overtures to Verdi's "I Vespri Siciliani" and to "Norma."

Each singer has at least one aria in which she is at her very best.

Price's is one of the greatest of soprano arias, "Pace, pace, mio Dio," from Verdi's "Forza del Destino." You can usually tell how a performance is likely to go by the second note, which is the bottom of that grueling descending octave on the word "pace" -- peace. It is perfect here. The huskiness that had impeded Price's coloring of her sound earlier in the evening is gone, and the range of hues is extensive. Her legendary soft highs are true and clear. And the intensity of the phrasing is up to her highest standards. It may not quite be the most precise "Pace, pace" this listener has heard from Price, but it is the most powerful. The ovation from the Met audience is furious, the greatest of the night. And on the third curtain call, the camera catches something that is rare with Price. Her eyes seem to be welling with tears, and she lowers her head, turns and leaves the stage looking down, instead of at her usual queenly tilt.

Horne has many grand moments, none more so than in the aria "Vivi, tyrano" from "Rodalinda." Few arias can have this many runs and scales and leaps. Only Horne could handle the music with such a combination of power and accuracy. Voices this big just aren't supposed to be able to move this fast.

The "Norma" duet is the musical climax of the evening. For one thing, it is one of the sublime soprano-mezzo passages in music, and also Adalgisa is one of Horne's grandest roles. So it may seem strange to focus on Price's Norma, but it is one of opera's great might-have-beens. A recording of "Casta diva" several years ago left the suggestion that Price might have been right to pass up the role. Her singing in the duet suggests the opposite; it has a fullness, intensity and tenderness that utterly eclipse the recent gander at "Norma" by Renata Scotto. Certainly, the coloratura side of "Norma" would have been difficult for Price. She does have a few strained moments in the duet. But she should have sung "Norma," and recorded it.

Other highlights: Horne's patter aria from Meyerbeer's "Les Huguenots"; Price in that little aria from Puccini's "La Rondine" that has practically become a trademark for her.

The physical interaction between the two singers all through the evening is good television. For example, after the "Norma" duet, they first applaud each other and then embrace. They seem to be carried away. And you will be, too.

The program will be simulcast on WETA-FM (90.9).