* When the Oakland-based women's ensemble Kitka performs at Trinity Cathedral next Sunday, it will also be introducing a wrinkle into its winter song program: instrumental accompaniment.

"They will make our upcoming concerts very special," said Shira Cion, one of Kitka's eight singers and executive director of the 25-year-old group. "The players will be Rumen Shopov, a Bulgarian tambra player (the tambra is a pear-shaped mandolinlike folk lute), who will also play bouzouki and percussion. Kaila Flexer, producer of the Bay Area's Klezmer Mania Festival, will play violin with us, and hand-drum player Tobias Roberson will play tambourine and frame drums. He's very fiery and exciting."

Kitka specializes in music from Eastern Europe. The group sings in 12 languages, tours extensively and has several recordings, including the new "Wintersongs" (on the Diaphonica label).

"Our research for new music is person-to-person, singer-to-singer," Cion said in a telephone interview from her office in Oakland. "We have some wonderful contacts in the global Eastern European community. As we travel around, we always meet people at concerts who ask if we'd be interested in music they know - and we always say, 'Yes!'

"One of the things that really draws us to this repertoire is that it comes out of an agricultural, village culture and it is very natural. It talks about trees, the sky, the earth and, of course, the divinity of the Virgin Mary. But the folk carols especially are very earthy in their feeling, and we really love that."