Insen is the second album in an ongoing collaboration between Japanese composer Ryuichi Sakamoto and German electronic artist Carsten Nicolai (here credited as Alva Noto). The album's core sound is a blend of Sakamoto's impressionist piano melodies and Nicolai's digitally processed beats and sounds. Released in 2005 by Nicolai's Raster-Noton label, it follows the duo's debut album Vrioon, which was named album of the year in 2004 by The Wire magazine.