Drawn together by a shared love of metal and prog rock, Riverside were founded in 2001 in Warsaw, Poland, by Mariusz Duda (vocals, bass, guitar), Piotr Grudzinski (guitar), Piotr Kozieradzki (drums), and Jacek Melnicki (keyboards). The quartet members intended to use their backgrounds in metal to explore new territory in prog rock along the lines of Dream Theater and Tool, creating spacious and experimental music with a metal edge. Even before their first record was finished, Riverside began to experience creative differences, with Melnicki (who was later replaced by current keyboard player Michal Lapaj) splitting from the group to pursue his own studio projects in 2003. Later that year, the band issued its full-length debut, Out of Myself, which was released the following year in the U.S. on Laser's Edge. After the success of their first record, the bandmembers got back to work on new material. In 2005 they released the EP Voices in My Head, gaining the attention of InsideOut, which released their second album, Second Life Syndrome, later that year. In 2007, after a European tour in support of Dream Theater, the group released Rapid Eye Movement. In 2009 they put out another studio record, Anno Domini High Definition (on Mystic Productions), which quickly became the best-selling record in Poland.