At the Busch-Reisinger Museum today through Saturday

A DOUBLE BILL of religious operas may not be your idea of entertainment, but this year's Leverett House Opera Society offering is one of the best productions, musically and theatrically, in the last few years at Harvard. The two plays were written 800 years apart. The Play of Daniel in 12th century France, Benjamin Britten's Curlew River several years ago in England. They make a fascinating pair, for both are parables for church performance, and both employ stylized musical and theatrical means to illustrate the parable with force.

The differences, however, are greater than the similarities. The Play of Daniel is an anonymous creation, with roots in folksong and in ecclesiastical chant. It is alternately solemn and joyous, with a directness that is rare in music of any period. The format of the work is more formal than the kind of drama which we are accustomed to. Daniel is a simple re-telling of the Biblical narrative, and there is no more concern for unity of time and place or for psychological realism than in the original tale. The verses of the text are set to unchangingly strophic music, unable to portray any more than one simple emotion in each "song."

And yet, despite all the theoretical limitations of the genre. The Play of Daniel is full of a vitality which is often lacking in the more pretentious art-works of our own century. At times the language of the text even slides momentarily from the ecclesiastical into the vernacular, and this is even more true of the music which often speaks in a language so close to real life that it makes itself understood many centuries later.

Much of the success of The Play of Daniel can be attributed to the efforts of the late Noah Greenberg, an American musicologist and director of the New York Pro Musica until his death. The current version of The Play of Daniel was made by Greenberg for the Pro Musica's performance at The Cloisters in New York. Although listed as an "adaptation." Greenberg's version is in fact a true re-creation. The orchestration and the distribution of vocal lines are entirely Greenberg's, for the original manuscripts of Daniel contain no more than the melodies and text. Greenberg's contribution is as imaginative as it is scholarly, and the scholarship is always-refreshingly-below the surface. In short, Greenberg managed to infuse life into this textbook relic but never forced his own personality on it.

Benjamin Britten's Carlew River is in many ways the direct antithesis of The Play of Daniel. Contrasted with the spontaneity of Daniel. Britten is extremely self-conscious and studied. The libretto, by William Plomer, based on a Japanese Noh-play, presents the story of a madwoman in search of her lost son, in straightforward, narrative manner. It is the music however, not the libretto, which is responsible for the overly calculated effect of the work as a whole. Through his use of a highly declamatory vocal style, with jagged melodic lines. Britten concentrates attention of presentation of the words at the expense of emotional projection. Certainly this is intentional, for every aspect of the work-from the choral chants to the subtle orchestral effects-contributes to the "objective" character of the opera. Whereas Daniel is warm and human within a framework of objectivity, Curlew River strives for a ritualized coldness-and attains it. A musician will find much to admire in Britten's craft and attention to detail. Curlew River is, however, not a work to love, as one can love The Play of Daniel. It has its audience, of course, but that audience is a more limited one than Britten should be aiming for.

THE PRODUCTION of the two works is admirable in nearly every respect. The Britten, in fact, receives the better performance, which is fortunate, for it needs the best possible performance to come off at all. The singers are unusually attentive to the pronunciation of the English libretto and project their parts with authority. Special mention should be made of David Evitts, who gives an intensity to the role of the Ferryman which surpasses even the excellent work of the other principals: James Paul, Robert Toren, Martin Kessler, and the talented boy soprano William Wright.

The cast of Daniel is more uneven, but again one singer stands out. His name is Lawrence Bakst, and he possesses one of the most attractive and effortless tenor voices around. It would be good to hear him more often in the Cambridge area. The other lead singers were generally effective, with Chalyce Brown an especially striking Queen. The chorus also sang well, but their acting was only to varying degrees appropriate. The entrance of the Queen's seven attendants, all smiling like airline stewardesses, was more appropriate to a Miss America pageant than a medieval pageant-opera.

With this minor exception, both operas received topnotch performances. The costumes were excellent, and so were the instrumentalists. (Hats off to Cyrus Stewart for his virtuoso performance of the horn part in Curlew River. ) The main credit, however, must go to Martin Kessler, musical director of both works, and to Wakeen Ray-Riv (choreographer in the Britten) and Charles Heckscher (director of Daniel ). Most of all, they deserve our gratitude for producing these seldom heard works and, even more, for giving them the performance they deserve.