Opera lovers are still divided on the merits of opera in English. The purists maintain that librettos are usually poor and translations worse--the main thing, they say, is the music. Others feel that the text is also worth understanding, since after all, the composer did expect the audience to know what is happening. As an experiment with opera in English, the New England Opera Company is currently offering on alternate nights this week two Mozart operas, Cosi Fan Tutti and Don Giovanni.

Cosi is particularly suited to translation because of its talkiness. And while the text used by director Boris Goldovsky has its disappointing moments, these are more than compensated for by the immediacy of the humor and understanding of the 18th century intention. The story centers around two army officers Guglielmo and Gernando and their philosopher-friend Don Alfonso. The Don, challenging the fidelity of the soldiers' betrothed, proves to them the fundamental frailty of human nature.

Mac Morgan and David Loyd play the parts of the soldiers and suitors with gusto making the most of every movement. Don Alfonso is properly sententious expounding 18th century morals, although his voice occasionaly gets lost. Nancy Tricky as the more adventurous and less constant of the betrothed is charming with a pleasant touch of worldliness. Her counterpart Jacqueline Bezinet, however, at times makes the ridiculous even more ridiculous. She is a follower of the mouth stretching school of acting and her contortions tend unduly to travesty the text.

The other presentation is a delightful version of Don Giovanni, that suave master of conquests--some 1003 in Spain we are told. In Mozart's opera the action covers just one day, but the Don tries like the devil to up his total by four or more. Naturally, he ends up with the devil himself and sinks out of sight to the accompaniment of the Underworld's trombones and smoke.

The production, a masterful combination of "theater" with "opera," brings new energy to the stage, and the principles well fulfill Mr. Goldovsky's goal by adding acting ability to singing talent. Kenneth Smith is dashing and powerful at the Don, who is humorously charming, clear voices, particularly the coquettish Joan Noynagh (Zerlina) and Adele Addison (Donna Anna).

With the lines in English a few of the usually "dramatic" Italian phrases sound a bit peculiar. For example, the young maid has finished a long sorrowful song about her mistreatment by the bawdy Don, and her gallant suitor warbles "Ohhh, a piteee." These are the exceptions however and this fine presentation, like Cosi, is highly enjoyable.