Sound Horizon began with Revo releasing his music creations on the internet on his website in the late 1990s. In 2001, Sound Horizon participated in Comic Market as part of a dōjin music circle and released their first story CD, Chronicle, an all-instrumental track CD, with occasional narration, background chorus and sound effects. The inclusion of actual singing began from their second release onwards. Their subsequent works were released at Comic Market and M3. Sound Horizon's first major release was in 2004, with the albumElysion ~Rakuen e no Zensōkyoku~. Their first maxi-single, "Shōnen wa Tsurugi o...", which was released in 2006, includes "Shūtan no Ou to Isekai no Kishi ~The Endia & The Knights~", the theme for the PlayStation 2simulation RPGChaos Wars, and "Kamigami ga Aishita Rakuen ~Belle Isle~", the opening theme for the MMORPGBelle Isle. Although Aramary was their main female singer through the Elysion album, her departure afterward led Sound Horizon's style to shift quite a bit, to having many vocalists, rather than just one main female one and one main male vocalist. Revo himself also tended to sing more often in the later albums, beginning with Roman. On September 3, 2006, Sound Horizon released the album Moira. The album featured Takashi Utsunomiya of TM Network as one of the vocalists. Moira debuted at No. 3 on the Oricon weekly album charts, selling over 45,000 copies in its initial week. Sound Horizon released the single "Ido e Itaru Mori e Itaru Ido" on June 16, 2010. The single featured guitarist Marty Friedman and VocaloidHatsune Miku, along with a beta voicebank for Vocaloid known as "Junger März PROTOTYPE β". In 2012, Revo began a new project called Linked Horizon, beginning with his work on the score for the Nintendo 3DS game , a series of EPs and album. In 2013, Linked Horizon performed the first, second, third and fifth opening themes, as well as the fourth ending theme, for the anime adaptation of Attack on Titan along with a series of EPs and albums. In June 2014, Revo also composed the first opening theme of Sailor Moon Crystal, "Moon Pride".
