Within a span of three weeks and two days. Washington is soon going to be able to hear. In two of the world's largest churches, two of the largest choral works ever written. Both of them by the same man: Hector Berlioz.

On Friday at 8:30 p.m. Robert Shafer will conduct the Berlioz "Te Deum" in the Shrine of the Immaculate Conception. On sunday. March 11. at 4 p.m., Paul Callaway will conduct the Berlioz Requiem in Washington Cathedral. Both churches are vastly larger than those in which these works were first performed. But both have long reverberation times and a sense of immense space that will frequently add unusual splendor to the composer's huge concepts.

Berlioz himself conducted the premiere of the "Te Deum" in the Parisian church of St. Eustache in 1855. It was the only complete performance of the work he ever conducted. He was supper-delighted with the results.

"The Te Deum was performed today with the most magnificent precision, Berlioz wrote to his friend Franz Liszt within hours after the premiere. "It was colossal. Babylonian. Ninivite... a scene from the Apocalypse."

Berlioz was no stranger to vast resources in music. Years before the "Te Deum" he had written in the Requiem for that astonishing choir of 16 kettle drums plus four brass choirs surrounding the orchestra-chorus area.

If we are to believe Berlioz account of the first performance of the Requiem in Les Invalides.We find there his reason for taking personal charge of the premiere of the "Te Deum." Berlioz claimed. after the first performance of the Requiem that the conductor. Herbeck. chose "the most crucial monent in the entire score" to take a leisurely pinch of snuff, and in doing so, to endanger the tricky change in rhythm at perecisely that point. Berlioz said that it was only by his own leaping forward to seize the baton form Herbeck and conducting the next few measures himself that a catastrophe was avoided.

There are major differences between the two great works. dictated by the differences in texts. In his own comparison of two of the grander episodes. Berlioz said he thought he had surpassed. at the lines "Judes crederis" of the "Te Deum." the stupefying effect he created in the "Tuba mirum" of the Requiem. What always needs to be reiterated before any performance of either of these works is that much of their greatness lies not in the huge quantities of sound Berlioz could conjure up. but the marvels of quiet passages that occupy more than half of each work. The remarkable sonorities of flutes and trombones accompanying the tenor solist in the "Sanctus" of the Requiem are only one illustration.

The differences in the scores touch both instrumental and choral aspects of the music. Where no organ is required for the Requiem, an important facet of the "Te Deum" is the dialogue between the orchestra and the organ, which Berlioz called "Pope and Emperor, speaking in dialogue from opposite ends of the nave." an effect easily obtained in the Shrine with its large antiphonal organs.The "Te Deum" also calls for triple chorus and children's chorus, neither of which are stipulated for the Requiem. Both works use only a tenor as soloist.

No composer was more scrupulous about the way his music was to be performed than Berlioz. Like Wagner, he knew precisely the effect that could be achieved if his directions were correctly carried out.

He was insistent that the four added brass choirs in the Requiem should be placed at the four points of the compass, around the other performers, and not, as they all too often are, from some distant corners of the building in which the music is being heard.

He was as particuair about the "Te Deum." insisting that "the orchestra and choir must be placed at the extreme end of the church opposite the organ. If the conductor has no electric metronome (!), with which to keep in immediate communication with the organist, a sub-conductor must be placed in the organ loft. The childeren's choir." he continued, "as nemerous as possible nd separated from the other two choirs. Should be raised on a platform not too far from the orchestra. Two or three choirmasters will be required to lead it and communicate the conductor's beat."

The "Te Deum" was special favorite of Sir Thomas Beecham's, who once told me that he had conducted it "much more often" than the Requiem. He also made a recording of it which still stands as a model in the grandeur of its conducting.

Neither work is heard over-frequently in any city in any season. Their outsized requirements make it difficult to present them as a regular matter. It is interesting that Washington will hear the Requiem later in the spring, when it is included in the Berlioz Festival at the Kennedy Center in May. It is, however, the ambience of the two large churches that stand on opposite hills in Washington, the Shrine and the Cathedral, that can give each of these grand scores a special measure of sound and impact. It is likely that Berlioz would have liked the idea of his largest works being heard in both places.