Jews are used to having their synagogues transformed into courts of law on Kol Nidre. But this year, Congregation Netivot Shalom also will become a laboratory.

That’s because on Erev Yom Kippur a newly written machzor (High Holy Days prayerbook) will have its first trial run at the Berkeley-based Conservative synagogue. It is one of only six congregations nationwide to test this preliminary edition — a machzor-in-progress — which includes only the portion for the Kol Nidre service.

Why Netivot Shalom? Because its head rabbi, Stuart Kelman, is one of the committee members responsible for compiling, writing and editing what will be a new High Holy Day machzor for the Conservative movement.

It’s the first revised High Holy Day siddur since the early 1970s, notes Kelman, adding that the time is right for a makeover.

“Every generation needs its own machzor,” he says. “Sensitivities change, language changes and there are new ways of expressing oneself that lend themselves to a common idiom.”

Kelman was one of 10 in a committee formed by the Conservative movement’s Rabbinical Assembly, which has met monthly for five years to compile the prayerbook. Each member brought his or her own personal strengths to the project, from Hebrew grammar to refined English prose, and each was assigned a particular section of the machzor.

For Kelman, that section was the Sh’ma and its blessings. “It was my responsibility to give a first shot at translation, commentary and the readings,” he says.

Conservative Jews nervous about radical changes in the new machzor can relax. Kelman says all of the traditional Hebrew liturgy has been retained. With an elegant graphic design that somewhat resembles pages from the Talmud, the new machzor includes Hebrew, new English translation and transliteration (a first for a Conservative siddur), as well as readings and commentary in the margins.

Other innovations include selections from Sephardic liturgy and the reinstitution of old prayers removed from the last machzor.

“We were trying to do something that would appeal to a range,” says Kelman.

The committee also chose not to translate certain terms like “Adonai,” preferring to let the unique character of the original Hebrew speak for itself.

Eminently qualified as the committee members may be, they are finding the project is an intellectual challenge. For Kelman, the Days process required a re-examination of the essence of the High Holy Day prayerbook.

“It forced us to confront a myriad of issues the machzor asks everyone to confront,” he says. “Redemption, reward and punishment: What do they mean? What does it mean to fix the world under the kingdom of the Almighty?”

Then the committee had to decide how faithful to be to the original Hebrew. “Do we want to change the Hebrew to fit a modern sensitivity,” he asked, “or reflect the original as much as possible (which is what we did)? We also had to make the English prayerful. And we wanted it to be as gender neutral as possible.”

The machzor project is nowhere near completed. The committee is still compiling and writing the rest. At this point, Kelman doesn’t see crossing the finish line any sooner than 2007. But he’s not complaining. He says the committee has been “one of the most exciting groups I ever participated in, both intellectually and emotionally.”

After Yom Kippur, Kelman will ask his congregants to fill out a four-page evaluation form to be mailed in later. If the reaction is anything like that of the Conservative rabbinate (every Conservative rabbi in America has received the book), he should get resoundingly positive feedback.

Still, he wants to hear from his congregants, and the sooner the better. Jokes Kelman, “I will tell people, ‘You have until the end of Sukkot.’ That’s it!”