By Alexis Simpson American reviews of the Icelandic band Sigur Rós most always include such accurate words as ethereal, spiritual, and haunting. His Detroit show was certainly avant-garde, an idealic experience, and even a bit high brow because the performance is akin to opera in the sense that the vocals are not in English. The group’s rare appearance in Detroit drew several months worth of buzz as fans grew more and more excited to see the awe-inspiring group in one of Detroit’s most iconic and beautiful venues. The stage setup was fairly simple but spread wide across the stage in order to accommodate many musicians and their instruments.  A wide video screen displayed…