Judaism has more than three branches now. The Metro story, "For Some Cantors, a Mission Beyond Music" [Sept. 19] reported on trends in cantorial training and practice by the three well-known Jewish religious groups: Orthodox, Conservative and Reform. But it doesn't mention Reconstructionist Judaism, now more than 60 years old and the fastest-growing branch of Judaism in the United States.

In the 1930s Rabbi Mordecai Kaplan recognized that many Jews were losing interest in religious observance, except perhaps for the high holidays. As a cogent philosopher and the leader of a congregation in New York, Rabbi Kaplan began to evolve a fresh approach to Jewish belief and practice. In "Judaism as a Civilization," published in 1934, he laid out the views he later elaborated in many books, articles and lectures.

His son-in-law, Rabbi Ira Eisenstein, now a resident of Silver Spring, synthesized Rabbi Kaplan's philosophy and turned it into a movement now practiced in more than 90 synagogues and fellowships across the country. It is fostered by the Jewish Reconstructionist Federation, a national body.

The essence of Reconstructionism is that Judaism is not just a religion but an evolving religious civilization. Reconstructionists believe in the importance of music, art, dance, the Hebrew language, a dedication to the State of Israel and a sense of Jewish peoplehood, along with a strong spirit of moral and ethical behavior and the maintenance of many traditional Jewish religious practices.

Reconstructionist Jews may hold varying theological views on the nature of God, though a central theme views God as a force for salvation in the universe and not an anthropomorphic being. More important, belief is only one of the three B's that Reconstructionists recognize. The other two are perhaps more crucial: belonging to the Jewish peoplehood and behaving as ethical human beings.

ISADORE SEEMAN

Silver Spring

The writer is president of the Reconstructionist Havurah of Greater Washington.