Theleast known side of Mstislav Rostropovich's multifaceted musical personality is also one of the most paradoxical and fascinating. Born in a country where atheism is established and promoted by the government as the official belief, where the suspicion that you worship God can get you into serious trouble, he, like his friend Aleksandr Solzhenitsyn, somehow became a devout member of the Orthodox Church.

Aneloquent testimony to this fact has just arrived from Paris in the form of a compact disc (Erato ECD 75319) containing Rachmaninoff's "Vespers," Op. 37. In the spacious acoustics of the Washington Cathedral (for once, exactly right for the music) Rostropovich conducts the Choral Arts Society in a celebration not only of the mysteries of faith but also of the enormous musical potential of massed, unaccompanied human voices.

Many of the melodies in this hour-long meditation are traditional, some dating back to the Middle Ages. They are enriched by Rachmaninoff's harmonies and "vocal orchestration." But for this work, the composer -- whose style is usually intensely personal and immediately recognizable -- has merged his art seamlessly into traditional ideals and practices. The music sounds as though it was created not by an individual but by a whole people -- as, indeed, it was.

The Choral Arts Society sings beautifully under Rostropovich's direction, producing a rich, well-controlled and exquisitely balanced tone. The soloists, mezzo-soprano Maureen Forrester and tenor Gene Tucker, are both excellent, but the major revelation on this disc is that Rostropovich is such a fine conductor of unaccompanied choral music. Much of the credit goes to Norman Scribner, who has made his chorus so expert and versatile, but Rostropovich handles this "instrument" as capably as his cello or the National Symphony Orchestra.

How it happened that a French recording company came to Washington to record an American chorus singing Russian music is a long, complicated story. But part of the answer is that Washington is only one of Rostropovich's homes; he is equally at home in Paris, where Erato has its headquarters, and he is viewed by Parisian music-lovers with the same kind of affection he receives here. When he celebrated his 60th birthday March 27, he did so in Washington, leaving the Parisian celebration until a bit later. To mark the occasion, Erato issued four records that have now reached the United States just in time for Rostropovich's return to open the NSO's subscription season.

Two of the records focus on Rostropovich in his best known role, as a virtuoso soloist on the cello. The fourth presents him as a conductor, interpreting the orchestral music of a personal friend and mentor, Sergei Prokofiev. The Rachmaninoff "Vespers" will have the most interest for Washingtonians, but all four discs are well worth knowing.

Rostropovich & Penderecki

Krzysztof Penderecki, who will be in Washington to conduct the NSO later this season, may be the most interesting composer alive; certainly he is one of the top three or four. In his Second Cello Concerto, now available on Erato ECD 75321, the solo part is tailored precisely to the skills and personality of his friend Rostropovich, to whom it is dedicated. Rostropovich gave the premiere performance in 1983 and has since made it a basic part of his repertoire.

The music is highly dramatic, technically demanding and emotionally powerful. It may be resisted by those who habitually resist contemporary music, but it is unquestionably a masterpiece.

This is the definitive recording, with Rostropovich unleashing his formidable technique and the composer conducting the magnificent Philharmonia Orchestra. The record is filled out with an excellent performance of Penderecki's fascinating Partita for concertante harpsichord, electric guitar, bass guitar, harp, double bass and orchestra.

Halffter's Poetry for Cello

Rostropovich's technique and personality are also the focus of the Cello Concerto No. 2 by Cristobal Halffter, Spain's leading composer. Halffter sometimes indulges in microtonal harmonies, but he also favors large, spectacular orchestral effects and virtuoso solo playing.

The work is dedicated to Rostropovich but inspired by the great Spanish poet Federico Garcia Lorca, and some of the mystery and emotive power of Lorca's poetry has found its way into this music. On Erato ECD 75320, Rostropovich plays with precision and panache, and Halffter conducts the Orchestre National de France expertly.

Two Symphonies of Prokofiev

Finally, on Erato ECD 75322, Rostropovich is presented leading the Orchestre National de France in Prokofiev's fourth and seventh symphonies -- part of a complete Prokofiev cycle he is recording for Erato. These are not the composer's most famous symphonies, but they are among the purest embodiments of his lyric spirit, without the enfant terrible brashness that flavors so much of his music. Often in Prokofiev one senses a sort of self-consciousness, a calculated effort to make striking effects. In these two works, he is free of such mannerisms; it appeals immediately and deepens its appeal with repeated hearings.

To estimate a performer's depth, listen to how he handles relatively quiet, apparently uneventful passages. Rostropovich's growth as a conductor during the last 10 years can be measured by his mastery of this music, which is brightly colored, superbly organized and highly communicative in his interpretation, even without the cheeky wit and spectacular effects found in some of Prokofiev's other music.