ULYANOVSK: Ksenia and Alexandra, both 19, met each other in psychology class at university and started an acoustic duo five months ago. They play cover songs by groups like Cold Play and Armstrong in pubs and bars in Ulyanovsk. They call their duo 'Sunday.' ''We thought for a long time about what to call ourselves, but we couldn't find something that fit,'' said Alexandra, whose parents and brother play instruments. Then one day, they auditioned at a pub. The pub's art director commented positively about their music, using a Russian word that can be translated as cheerful or sunny. ''Therefore, they recommended we call ourselves Sunday, because our music is bright and warm like a sunny day.''