Sika is a four-piece band out of Minneapolis, Minnesota. It is difficult to classify their music (I know, I know, you've heard that before), because each song is different than the last, and the band vigorously eschews any boundaries but their own collective taste.
There are, however, some common elements to name. Broadly defined, Sika is indie-rock, with all the ambiguity that term brings these days. Their influences include such diverse bands as Muse, Radiohead, Sigur Ros, Depeche Mode, In Flames, and Rammstein. Sika has been described as "Eclectic border jumping indie post-rock ambiguity", and that seems as good a classification as any.
Keyboards play a strong role and can be heard on every song, without exception, but never in quite the same way from one to the next. The guitar playing ranges from lush, swelling ambience to Cure-like melodies, all the way to crunching, heart-pounding distortion. Sika's drum style is also rather diverse: with influences from rap to Radiohead (if you've never paid close attention to their drumming, give them another listen), it is punctuated by syncopation and sometimes mismatched time signatures.
Aleksey's vocal style, not surprisingly, also comes from the band's biggest influences listed above, mostly Thom Yorke and Matthew Bellamy, but also a touch of Davey Havok now and again. His generally high-pitched, often falsetto leads are complemented by harmonies from the rest of the band. But don't expect to hear the same voice on every song. The band often trades off lead-singing duty between certain songs, and even sometimes within the same song.
Sika is never satisfied with itself. Because of this the band changes continuously (hopefully for the better), and may even surprise you once in a while.