There will be a concert this evening of Russian liturgical and folk music sung by 23 children and young people of the Cathedral Choir of Krasnoyarsk in Siberia. The concert will be held at the Church of Our Saviour (Park Avenue at 38th Street) and begins at 5:30 p.m. These highly trained singers have sung in Spain, Japan, Switzerland, France, and Italy, and are now on their U.S. tour. Admission is free and a voluntary offering may be left in the collection box in the rear of the church.